Method for resumption of an application session with a very dynamic and very large state in a standby intermediary device when the primary device fails

ABSTRACT

The present disclosure is directed towards systems and methods of maintaining a session via an intermediary device. A first device intermediary to a client and a plurality of servers receives a packet of a session. The packet of the session includes application protocol data and application session metadata used to maintain a state of an application accessed via the session. The first device marks a session state of the session to an update state. The first device determines that a second device intermediary to the client and the plurality of servers is in a ready state and the session state of the session is in the update state. The first device forwards the application protocol data and the application session metadata of the packet to the second device to maintain, on the second device, the same state of the application accessed via the session provided by the first device.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is a continuation of, and claims priority to andthe benefit of U.S. patent application Ser. No. 14/927,600, titled“METHOD FOR RESUMPTION OF AN APPLICATION SESSION WITH A VERY DYNAMIC ANDVERY LARGE STATE IN A STANDBY INTERMEDIARY DEVICE WHEN THE PRIMARYDEVICE FAILS,” and Oct. 30, 2015, the contents of all of which arehereby incorporated herein by reference in its entirety for allpurposes.

FIELD OF THE DISCLOSURE

The present application generally relates to maintaining a session viaan intermediary device. In particular, the present application relatesto systems and methods for resuming an application session with a large,dynamic state maintained in a standby intermediary device when theprimary intermediary device fails.

BACKGROUND OF THE DISCLOSURE

A client device can access or use an application provided or executed bya server via an intermediary device that is intermediary to the clientdevice and the server. The intermediary device can establish a sessionbetween the client device and the server to provide access to theapplication executed by the server. The state of the application canchange during the session as the client device interacts with theapplication executed by the server. However, if the intermediary devicefails or becomes unresponsive, it may be challenging to maintain thesession state information and provide the client with access to theapplication executed by the server. Thus, it may be challenging toefficiently provide high availability of application resources ascomputing devices in the computing environment fail or becomeunresponsive.

BRIEF SUMMARY OF THE DISCLOSURE

The present disclosure is directed towards systems and methods formaintaining a session via an intermediary device. In particular, thepresent solution relates to systems and methods for resuming anapplication session with a large, dynamic state maintained in a standbyintermediary device when the primary device fails.

An appliance pair can be deployed as an active-standby appliance pairthat is intermediary to a plurality of clients and a plurality ofservers. For example, the appliance pair can include a first device thatis in an active mode in which the first device actively servicesrequests from a client by parsing packets received from the client,providing the client with response packets received from the server, orotherwise providing the client with access to an application executed bya server. In some cases, the first device of the appliance pair that isinitially configured to be in the active mode can be referred to as theprimary device. The appliance pair can include a second device that isinitially configured to be in standby mode. The second device may notactively service requests from the client device. The second device maybe referred to as the secondary device because it is in standby mode anddoes not actively service requests received from the client or provideresponses received from the server to the client. If the primary devicefails, becomes unresponsive, is brought down for scheduled maintenanceor is otherwise unable to process packets between the client device andthe server, the secondary device can become the new primary device andservice the client device by processing client requests.

The appliance pair (or the first device or the second device thereof)can be configured to perform deep packet inspection on the applicationtraffic. The application traffic can refer to packets received from theclient that are to be processed or provided to the server, or packetsreceived from the server that are to be processed or provided to theclient. The appliance can perform deep packet inspection to gainvisibility into the session state or to facilitate troubleshooting oridentify problems or issues. In such a deployment, if the primary devicefails and the secondary device becomes the new primary device, theclient device accessing the application or desktop session over anapplication server protocol (e.g., Independent Computing Architecture“ICA”) may be disconnected from the session. The client device may haveto then re-login to the session to access the application or desktopsession provided by the server via the intermediary device.

Systems and methods of the present solution can seamlessly resume theaffected session on the new primary intermediary device. By seamlesslyresuming the affected session on the new primary intermediary device,the client device may be unaffected by the failure of the originalprimary intermediary device causing the standby secondary to become thenew primary.

For example, a computing network can provide high availability ofapplication resources using a network intermediary device (e.g.,NetScaler® manufactured by Citrix Systems, Inc. of Ft. Lauderdale, Fla.)that is deployed in an active-standby appliance pair. In anactive-standby appliance pair, a first intermediary device activelyservices client device, while a second intermediary device is maintainedin a standby mode. For example, and in some embodiments, a firstintermediary device can be in an active mode and can parse and processan application session, such as an ICA session. The first intermediarydevice can be paired with a second intermediary device that is in astandby mode. The first intermediary device can maintain significantstate information, which may be dynamic and change on a per-packet basis(e.g., as each packet is being processed). If the first intermediarydevice fails, then the standby device can become the new primary device.The secondary device can become the new primary device and resume thesession without affecting the user experience provided by the clientdevice.

The appliance pair (e.g., the first intermediary device, secondintermediary device, or active-standby pair of intermediary devices) canbe configured to provide visibility into the session between the clientdevice and the server providing the application. For example, theintermediary device can provide visibility into the protocol (e.g., anICA protocol, or a high definition experience “HDX” protocol) fortroubleshooting or analytics purposes. To parse the protocol, anintermediary device of the appliance pair manages a large amount ofstate information within the device. This state information can include,e.g., information arising out of parsing an ICA protocol, parsing acommon gateway protocol (“CGP”), decrypting and re-encrypting ICAframes, or decompressing ICA Frames. As a result, the state informationmaintained by the intermediary device may be very large (e.g., 5megabytes, 50 megabytes, 100 megabytes, 500 megabytes, or 1 gigabyte),and this state information can change with one or more packets processedby the intermediary device (e.g., can change with every packetprocessed).

The primary intermediary device can maintain the state per session inmemory of the primary intermediary device. Because of the size of thestate that is updated on every packet, it may be challenging or notpossible for the primary intermediary device to share and update thestate in an external device (e.g. another intermediary device). If theprimary intermediary device cannot share and update the state in anexternal device, the state maintained in memory of the primaryintermediary device may be lost when the primary intermediary devicegoes offline. As the primary intermediary device goes offline,connections between the primary intermediary device (e.g., transmissioncontrol protocol “TCP” connections) can be reset. When connectionsbetween the client device and the primary intermediary device are reset,an agent executing on the client device may initiate a sessionreconnect. The new connection (e.g., TCP connection) established via thesession reconnect initiated by the agent of the client device can landon or be established via the new primary intermediary device (e.g., thesecond intermediary device that was previously in standby mode). If thisnew primary intermediary device does not have state information for thesession, the new primary intermediary may not be able to resume thesession. Systems and methods of the present solution can allow thesecond intermediary device (or secondary device) to maintain state onthe second device while in standby mode in tandem with the primaryintermediary device. Thus, when the primary intermediary device goesoffline and the secondary intermediary device takes over in the newprimary role, the secondary device can support and continue on with thesession reconnect initiated by the client agent.

In some embodiments, the primary intermediary device and the secondaryintermediary device can both be in a ready state. A ready state canindicate that a device is ready to parse packets that carry applicationprotocol data and application session metadata. During applicationlaunch, an agent executing on a client device can initiate a request toconnect via a protocol connection to a backend server or host via aprimary intermediary device. The primary intermediary device can detectthe request to initiate the connection and launch the applicationcorrespond to a new protocol connection, and the primary intermediarydevice can parse and process the request.

While the primary intermediary device parses and processes the requestor other data packets from the agent executing on the client device, theprimary intermediary device can detect that a secondary intermediarydevice is in the ready state. Responsive to detecting that the secondaryintermediary device is in the ready state, the primary intermediarydevice can mark the session in an update state and also forwardapplication protocol data and the application session metadatacorresponding to the request or the data packets to the secondaryintermediary device. The application protocol data and applicationsession meta data can be collectively referred to as application data.The application protocol data can refer to a high definition experience(“HDX”) protocol data. Application session data can refer to an HDXsession meta data. The secondary intermediary can receive theapplication data and parse the application data, or application protocoldata or application session meta data thereof.

Thus, by forwarding the application data from the primary device to thesecondary device and instructing the secondary device to parse the sameapplication protocol data as the primary intermediary device, systemsand methods of the present solution can maintain the same session statein both the primary intermediary device and the secondary intermediarydevice of the appliance pair. By maintaining the same session state inboth the primary and secondary intermediary devices, the secondaryintermediary device can seamlessly take over when the primaryintermediary device fails or otherwise becomes unresponsive. Forexample, when the primary intermediary device fails, all TCP connectionscan be reset. The agent executing on the client device sends a requestto establish a new CGP/ICA connection via a session reconnect process.The new connection can land on the new primary intermediary device(e.g., the former secondary intermediary device in standby mode). Thenew primary intermediary device can inspect, process, or analyze thesession reconnect connection to identify and retrieve the session stateinformation associated with this session reconnect. This session stateinformation may have been created and maintained by the new primarydevice when the new primary device was the secondary intermediary devicevia packet replay from the previous (e.g., original or initial) primaryintermediary device.

If, at some point in this process, the original primary intermediarydevice determines or detects that the secondary intermediary device(e.g., the standby device) is not in ready state (e.g., due to failureof the secondary intermediary, the secondary intermediary device beingunresponsive or offline due to scheduled or unscheduled maintenance),the primary intermediary device can mark the session in a down state ornot ready state. When the primary intermediary device marks the sessionin the down state, the primary intermediary device can stop, block,prevent, or cease forwarding the application protocol data orapplication session meta data to the secondary intermediary device.Thus, if the session in the down state, the primary intermediary devicedoes not forward application data to the secondary intermediary device.

If, at some later time, the primary intermediary device detects that thesecondary intermediary device is back online or back in a ready stateindicating that the secondary intermediary device is ready to parseapplication protocol data to maintain a session state in memory of thesecondary intermediary device, the primary intermediary device can markthe session in a session update state. Responsive to a transition of thesession state from the down state to the update state, the primaryintermediary device can push, provide, transfer, or otherwise forwardthe application protocol session state to the secondary intermediarydevice so as to bring the secondary intermediary device up-to-date. Forexample, the primary secondary device can push the complete applicationprotocol session state to the secondary intermediary device to bring thesecondary intermediary device up-to-date in a single communication.Thereafter, once the secondary intermediary device maintains a sessionstate in memory of the secondary intermediary device that matches thesession state in the primary intermediary device, the primaryintermediary device can continue to forward or replay application datato the secondary intermediary device to synchronize the session statemaintained by the secondary intermediary device in with the sessionstate of the primary intermediary device.

At least one aspect of the present disclosure is directed to a method ofmaintaining a session via an intermediary device. The method can includemaintaining a session via an appliance pair that includes a firstintermediary device and a second intermediary device. In someembodiments, a first device intermediary to a client and a plurality ofservers receives a packet of a session. The packet of the sessionincludes application protocol data and application session metadata usedto maintain a state of an application accessed via the session. Thefirst device marks a session state of the session to an update state.The first device determines that a second device intermediary to theclient and the plurality of servers is in a ready state and the sessionstate of the session is in the update state. The first device forwardsthe application protocol data and the application session metadata ofthe packet to the second device to maintain, on the second device, thesame state of the application accessed via the session provided by thefirst device. The first device can forward the application protocol dataand the application session metadata to the second device responsive todetermining that the second device is in the ready state and the sessionis in the update state.

The ready state of the second device can indicate that the second deviceis ready to parse the application protocol data and the applicationsession metadata to maintain, in memory of the second device, the samestate of the application accessed via the session provided by the firstdevice. The first device can be in an active mode to actively servicethe client, and the second device can be in a standby mode. The firstdevice and the second device can form an active-standby pair.

The first device can parse the packet to actively service the clientduring at least a portion of the session. The second device can be in astandby mode and maintain, in memory of the second device, the state ofthe application accessed via the session provided by the first devicewhile the first device actively services the client.

The first device can set a first value to a parameter of the session.The first value can indicate to the first device to forward theapplication protocol data and the application session metadata to thesecond device responsive to determining that the second device is in theready state. The first device can forward the application protocol dataand the application session metadata of the packet to the second deviceresponsive to the first value of the parameter. The second device canmaintain, in a session data structure stored in memory of the seconddevice, the state of the application accessed via the session providedby the first device. The second device can maintain the state of theapplication to match the state of the application accessed via thesession on the first device.

The second device can resume the session on the second device. Thesecond device can resume the session responsive to the first deviceentering an offline mode. The second device can resume the session withthe state of the application accessed via the session that matches thestate of the application accessed via the session on the first deviceprior to the first device entering the offline mode. When the firstdevice enters the offline mode, a first connection used for the sessioncan reset. The second device can then establish a second connection withthe client to resume the session.

The first device can establish the session between the client device anda server of the plurality of servers responsive to receiving logininformation from the client. The second device can resume the sessionresponsive to failure of the first device. The second device can resumethe session without the second device receiving the login informationfrom the client. In some embodiments, the second device can receive arequest from an agent executed by the client to reconnect the sessionresponsive to failure of the first device. The second device canretrieve the state maintained in memory of the second device. The seconddevice can resume the session with the state retrieved from the memory.

The first device can receive an indication to launch the application.The first device can receive the indication from the client. The firstdevice can be in an active mode to actively service the client.Responsive to the indication, the first device can initiate a connectionto a server of the plurality of servers. The server can be configured toexecute the application. The first device can establish the sessionbetween the client and the server to provide access to the applicationexecuted by the server. The first device can detect that the seconddevice is in the ready state. The first device can forward, to thesecond device, application protocol data and application sessionmetadata of packets received by the first device during the session. Thefirst device can forward the application protocol data and theapplication session metadata responsive to detecting that the seconddevice is in the ready state. The first device can forward theapplication protocol data and application session metadata to enable thesecond device to maintain, in memory of the second device, the state ofthe application accessed via the session while the first device parsesthe packets to provide access to the application executed by the server.

In some cases, subsequent to or after the first device forwards theapplication protocol data and the application session metadata to thesecond device, the first device can detect that the second device is notin the ready state. The first device can then set a second value of aparameter of the session to indicate to the first device to not forwardthe application protocol data and application session metadata to thesecond device. The first device can determine not to forward applicationprotocol data and application session metadata of a second packet of thesession received from the client. The first device can make thisdetermination responsive to the second value of the parameter.

In some cases, subsequent to determining not to forward the applicationprotocol data and the application session metadata of the second packet,the first device can detect that the second device is in the readystate. The first device can then push a complete session state to thesecond device. This complete session state can include the applicationprotocol data and the application session metadata of the second packetnot forwarded to the second device. The second device can then updatethe state of the application stored in memory of the second device withthe complete session state to match a current session state maintainedon the first device.

Another aspect is directed to a system to maintain a session via anintermediary. In some embodiments, the system can include a first devicethat is intermediary to a client and a plurality of servers. The firstdevice can include one or more processors and memory. The first deviceis configured to receive a packet of a session that includes applicationprotocol data and application session metadata used to maintain a stateof an application accessed via the session. The first device isconfigured to mark a session state of the session to an update state.The first device is configured to determine that a second deviceintermediary to the client and the plurality of servers is in a readystate and the session state of the session is in the update state. Thefirst device is configured to forward, to a second device intermediaryto the client and the plurality of servers, the application protocoldata and the application session metadata of the packet to the seconddevice to maintain, on the second device, the same state of theapplication accessed via the session provided by the first device. Thefirst device is configured to forward the application protocol data andthe application session metadata of the packet responsive to determiningthat the second device is in the ready state and the session is in theupdate state.

The first can be further configured to parse the packet to activelyservice the client during at least a portion of the session. In someembodiments, the system can include the second device configured tomaintain, in memory of the second device, the state of the applicationaccessed via the session provided by the first device while the firstdevice actively services the client. The second device can be in astandby mode.

In some embodiments, the first device can be further configured to set afirst value of a parameter of the session that indicates to the firstdevice to forward the application protocol data and the applicationsession metadata to the second device responsive to determining that thesecond device is in the ready state. The first device can be furtherconfigured to forward the application protocol data and the applicationsession metadata of the packet to the second device responsive to thefirst value of the parameter. The second device can be furtherconfigured to maintain, in a session data structure stored in memory ofthe second device, the state of the application accessed via the sessionprovided by the first device to match the state of the applicationaccessed via the session on the first device.

The second device can be further configured to resume, responsive to thefirst device entering an offline mode, the session on the second devicewith the state of the application accessed via the session that matchesthe state of the application accessed via the session on the firstdevice prior to the first device entering the offline mode. The seconddevice can be further configured to receive a request from the client toreconnect the session responsive to failure of the first device. Thesecond device can be configured to retrieve the state maintained inmemory of the second device. The second device can be configured toresume the session state retrieved from the memory.

In some embodiments, the first device can be further configured toreceive, from the client, an indication to launch an application. Thefirst device can be in an active mode to actively service the client.The first device can be configured to initiate, responsive to theindication, a connection to a server of the plurality of servers. Theserver can be configured to execute the application. The first devicecan be configured to establish the session between the client and theserver to provide access to the application executed by the server. Thefirst device can be configured to detect that the second device is inthe ready state. The first device can be configured to forward to thesecond device application protocol data and application session metadataof packets received by the first device during the session. The firstdevice can forward the data responsive to detecting that the seconddevice is in the ready state and to enable the second device tomaintain, in memory of the second device, the state of the applicationaccessed via the session while the first device parses the packets toprovide access to the application executed by the server.

The first device can be further configured to detect, subsequent toforwarding the application protocol data and the application sessionmetadata of the packet to the second device, that the second device isnot in the ready state. The first device can be configured to set asecond value to a parameter that indicates to the first device to notforward the application protocol data and the application sessionmetadata to the second device. The first device can be configured todetermine, responsive to the second value of the parameter, not toforward application protocol data and application session metadata of asecond packet of the session received from the client.

The first device can be further configured to detect, subsequent to thedetermination not to forward the application protocol data and theapplication session metadata of the second packet, that the seconddevice is in the ready state. The first device can be configured toprovide a complete session state to the second device. The completesession state can include the application protocol data and theapplication session metadata of the second packet not forwarded to thesecond device. The second device can be configured to update the statestored in memory of the second device with the complete session state tomatch a current session state maintained on the first device.

BRIEF DESCRIPTION OF THE FIGURES

The foregoing and other objects, aspects, features, and advantages ofthe present solution will become more apparent and better understood byreferring to the following description taken in conjunction with theaccompanying drawings, in which:

FIG. 1A is a block diagram of an embodiment of a network environment fora client to access a server via an appliance;

FIG. 1B is a block diagram of an embodiment of an environment fordelivering a computing environment from a server to a client via anappliance;

FIG. 1C is a block diagram of another embodiment of an environment fordelivering a computing environment from a server to a client via anappliance;

FIG. 1D is a block diagram of another embodiment of an environment fordelivering a computing environment from a server to a client via anappliance;

FIGS. 1E-1H are block diagrams of embodiments of a computing device;

FIG. 2A is a block diagram of an embodiment of an appliance forprocessing communications between a client and a server;

FIG. 2B is a block diagram of another embodiment of an appliance foroptimizing, accelerating, load-balancing and routing communicationsbetween a client and a server;

FIG. 3 is a block diagram of an embodiment of a client for communicatingwith a server via the appliance;

FIG. 4A is a block diagram of an embodiment of a virtualizationenvironment;

FIG. 4B is a block diagram of another embodiment of a virtualizationenvironment;

FIG. 4C is a block diagram of an embodiment of a virtualized appliance;

FIG. 5A are block diagrams of embodiments of approaches to implementingparallelism in a multi-core system;

FIG. 5B is a block diagram of an embodiment of a system utilizing amulti-core system;

FIG. 5C is a block diagram of another embodiment of an aspect of amulti-core system;

FIG. 6 is a block diagram of an embodiment of a cluster system;

FIG. 7A is a block diagram of an embodiment of a system for maintaininga session via an intermediary device; and

FIG. 7B is a block diagram of an embodiment of a method of maintaining asession via an intermediary device.

FIG. 8A is a flow diagram of an embodiment of maintaining a session viaan intermediary device.

FIG. 8B is a flow diagram of an embodiment of maintaining a session viaan intermediary device.

The features and advantages of the present solution will become moreapparent from the detailed description set forth below when taken inconjunction with the drawings, in which like reference charactersidentify corresponding elements throughout. In the drawings, likereference numbers generally indicate identical, functionally similar,and/or structurally similar elements.

DETAILED DESCRIPTION

For purposes of reading the description of the various embodimentsbelow, the following descriptions of the sections of the specificationand their respective contents may be helpful:

Section A describes a network environment and computing environmentwhich may be useful for practicing embodiments described herein;

Section B describes embodiments of systems and methods for delivering acomputing environment to a remote user;

Section C describes embodiments of systems and methods for acceleratingcommunications between a client and a server;

Section D describes embodiments of systems and methods for virtualizingan application delivery controller;

Section E describes embodiments of systems and methods for providing amulti-core architecture and environment; Section F describes embodimentsof systems and methods for providing a clustered appliance architectureenvironment; and

Section G describes embodiments of systems and methods for maintaining asession via an intermediary.

A. Network and Computing Environment

Prior to discussing the specifics of embodiments of the systems andmethods of an appliance and/or client, it may be helpful to discuss thenetwork and computing environments in which such embodiments may bedeployed. Referring now to FIG. 1A, an embodiment of a networkenvironment is depicted. In brief overview, the network environmentcomprises one or more clients 102 a-102 n (also generally referred to aslocal machine(s) 102, or client(s) 102) in communication with one ormore servers 106 a-106 n (also generally referred to as server(s) 106,or remote machine(s) 106) via one or more networks 104, 104′ (generallyreferred to as network 104). In some embodiments, a client 102communicates with a server 106 via an appliance 200.

Although FIG. 1A shows a network 104 and a network 104′ between theclients 102 and the servers 106, the clients 102 and the servers 106 maybe on the same network 104. The networks 104 and 104′ can be the sametype of network or different types of networks. The network 104 and/orthe network 104′ can be a local-area network (LAN), such as a companyIntranet, a metropolitan area network (MAN), or a wide area network(WAN), such as the Internet or the World Wide Web. In one embodiment,network 104′ may be a private network and network 104 may be a publicnetwork. In some embodiments, network 104 may be a private network andnetwork 104′ a public network. In another embodiment, networks 104 and104′ may both be private networks. In some embodiments, clients 102 maybe located at a branch office of a corporate enterprise communicatingvia a WAN connection over the network 104 to the servers 106 located ata corporate data center.

The network 104 and/or 104′ be any type and/or form of network and mayinclude any of the following: a point to point network, a broadcastnetwork, a wide area network, a local area network, a telecommunicationsnetwork, a data communication network, a computer network, an ATM(Asynchronous Transfer Mode) network, a SONET (Synchronous OpticalNetwork) network, a SDH (Synchronous Digital Hierarchy) network, awireless network and a wireline network. In some embodiments, thenetwork 104 may comprise a wireless link, such as an infrared channel orsatellite band. The topology of the network 104 and/or 104′ may be abus, star, or ring network topology. The network 104 and/or 104′ andnetwork topology may be of any such network or network topology as knownto those ordinarily skilled in the art capable of supporting theoperations described herein.

As shown in FIG. 1A, the appliance 200, which also may be referred to asan interface unit 200 or gateway 200, is shown between the networks 104and 104′. In some embodiments, the appliance 200 may be located onnetwork 104. For example, a branch office of a corporate enterprise maydeploy an appliance 200 at the branch office. In other embodiments, theappliance 200 may be located on network 104′. For example, an appliance200 may be located at a corporate data center. In yet anotherembodiment, a plurality of appliances 200 may be deployed on network104. In some embodiments, a plurality of appliances 200 may be deployedon network 104′. In one embodiment, a first appliance 200 communicateswith a second appliance 200′. In other embodiments, the appliance 200could be a part of any client 102 or server 106 on the same or differentnetwork 104,104′ as the client 102. One or more appliances 200 may belocated at any point in the network or network communications pathbetween a client 102 and a server 106.

In some embodiments, the appliance 200 comprises any of the networkdevices manufactured by Citrix Systems, Inc. of Ft. Lauderdale Fla.,referred to as NetScaler® devices. In other embodiments, the appliance200 includes any of the product embodiments referred to asWebAccelerator and BigIP manufactured by F5 Networks, Inc. of Seattle,Wash. In another embodiment, the appliance 205 includes any of the DXacceleration device platforms and/or the SSL VPN series of devices, suchas SA 700, SA 2000, SA 4000, and SA 6000 devices manufactured by JuniperNetworks, Inc. of Sunnyvale, Calif. In yet another embodiment, theappliance 200 includes any application acceleration and/or securityrelated appliances and/or software manufactured by Cisco Systems, Inc.of San Jose, Calif., such as the Cisco ACE Application Control EngineModule service software and network modules, and Cisco AVS SeriesApplication Velocity System.

In one embodiment, the system may include multiple, logically-groupedservers 106. In these embodiments, the logical group of servers may bereferred to as a server farm 38. In some of these embodiments, theserves 106 may be geographically dispersed. In some cases, a farm 38 maybe administered as a single entity. In other embodiments, the serverfarm 38 comprises a plurality of server farms 38. In one embodiment, theserver farm executes one or more applications on behalf of one or moreclients 102.

The servers 106 within each farm 38 can be heterogeneous. One or more ofthe servers 106 can operate according to one type of operating systemplatform (e.g., WINDOWS NT, manufactured by Microsoft Corp. of Redmond,Wash.), while one or more of the other servers 106 can operate onaccording to another type of operating system platform (e.g., Unix orLinux). The servers 106 of each farm 38 do not need to be physicallyproximate to another server 106 in the same farm 38. Thus, the group ofservers 106 logically grouped as a farm 38 may be interconnected using awide-area network (WAN) connection or medium-area network (MAN)connection. For example, a farm 38 may include servers 106 physicallylocated in different continents or different regions of a continent,country, state, city, campus, or room. Data transmission speeds betweenservers 106 in the farm 38 can be increased if the servers 106 areconnected using a local-area network (LAN) connection or some form ofdirect connection.

Servers 106 may be referred to as a file server, application server, webserver, proxy server, or gateway server. In some embodiments, a server106 may have the capacity to function as either an application server oras a master application server. In one embodiment, a server 106 mayinclude an Active Directory. The clients 102 may also be referred to asclient nodes or endpoints. In some embodiments, a client 102 has thecapacity to function as both a client node seeking access toapplications on a server and as an application server providing accessto hosted applications for other clients 102 a-102 n.

In some embodiments, a client 102 communicates with a server 106. In oneembodiment, the client 102 communicates directly with one of the servers106 in a farm 38. In another embodiment, the client 102 executes aprogram neighborhood application to communicate with a server 106 in afarm 38. In still another embodiment, the server 106 provides thefunctionality of a master node. In some embodiments, the client 102communicates with the server 106 in the farm 38 through a network 104.Over the network 104, the client 102 can, for example, request executionof various applications hosted by the servers 106 a-106 n in the farm 38and receive output of the results of the application execution fordisplay. In some embodiments, only the master node provides thefunctionality required to identify and provide address informationassociated with a server 106′ hosting a requested application.

In one embodiment, the server 106 provides functionality of a webserver. In another embodiment, the server 106 a receives requests fromthe client 102, forwards the requests to a second server 106 b andresponds to the request by the client 102 with a response to the requestfrom the server 106 b. In still another embodiment, the server 106acquires an enumeration of applications available to the client 102 andaddress information associated with a server 106 hosting an applicationidentified by the enumeration of applications. In yet anotherembodiment, the server 106 presents the response to the request to theclient 102 using a web interface. In one embodiment, the client 102communicates directly with the server 106 to access the identifiedapplication. In another embodiment, the client 102 receives applicationoutput data, such as display data, generated by an execution of theidentified application on the server 106.

Referring now to FIG. 1B, an embodiment of a network environmentdeploying multiple appliances 200 is depicted. A first appliance 200 maybe deployed on a first network 104 and a second appliance 200′ on asecond network 104′. For example a corporate enterprise may deploy afirst appliance 200 at a branch office and a second appliance 200′ at adata center. In another embodiment, the first appliance 200 and secondappliance 200′ are deployed on the same network 104 or network 104. Forexample, a first appliance 200 may be deployed for a first server farm38, and a second appliance 200 may be deployed for a second server farm38′. In another example, a first appliance 200 may be deployed at afirst branch office while the second appliance 200′ is deployed at asecond branch office’. In some embodiments, the first appliance 200 andsecond appliance 200′ work in cooperation or in conjunction with eachother to accelerate network traffic or the delivery of application anddata between a client and a server

Referring now to FIG. 1C, another embodiment of a network environmentdeploying the appliance 200 with one or more other types of appliances,such as between one or more WAN optimization appliance 205, 205′ isdepicted. For example a first WAN optimization appliance 205 is shownbetween networks 104 and 104′ and a second WAN optimization appliance205′ may be deployed between the appliance 200 and one or more servers106. By way of example, a corporate enterprise may deploy a first WANoptimization appliance 205 at a branch office and a second WANoptimization appliance 205′ at a data center. In some embodiments, theappliance 205 may be located on network 104′. In other embodiments, theappliance 205′ may be located on network 104. In some embodiments, theappliance 205′ may be located on network 104′ or network 104″. In oneembodiment, the appliance 205 and 205′ are on the same network. Inanother embodiment, the appliance 205 and 205′ are on differentnetworks. In another example, a first WAN optimization appliance 205 maybe deployed for a first server farm 38 and a second WAN optimizationappliance 205′ for a second server farm 38′

In one embodiment, the appliance 205 is a device for accelerating,optimizing or otherwise improving the performance, operation, or qualityof service of any type and form of network traffic, such as traffic toand/or from a WAN connection. In some embodiments, the appliance 205 isa performance enhancing proxy. In other embodiments, the appliance 205is any type and form of WAN optimization or acceleration device,sometimes also referred to as a WAN optimization controller. In oneembodiment, the appliance 205 is any of the product embodiments referredto as CloudBridge® manufactured by Citrix Systems, Inc. of Ft.Lauderdale, Fla. In other embodiments, the appliance 205 includes any ofthe product embodiments referred to as BIG-IP link controller and WANjetmanufactured by F5 Networks, Inc. of Seattle, Wash. In anotherembodiment, the appliance 205 includes any of the WX and WXC WANacceleration device platforms manufactured by Juniper Networks, Inc. ofSunnyvale, Calif. In some embodiments, the appliance 205 includes any ofthe steelhead line of WAN optimization appliances manufactured byRiverbed Technology of San Francisco, Calif. In other embodiments, theappliance 205 includes any of the WAN related devices manufactured byExpand Networks Inc. of Roseland, N.J. In one embodiment, the appliance205 includes any of the WAN related appliances manufactured by PacketeerInc. of Cupertino, Calif., such as the PacketShaper, iShared, and SkyXproduct embodiments provided by Packeteer. In yet another embodiment,the appliance 205 includes any WAN related appliances and/or softwaremanufactured by Cisco Systems, Inc. of San Jose, Calif., such as theCisco Wide Area Network Application Services software and networkmodules, and Wide Area Network engine appliances.

In one embodiment, the appliance 205 provides application and dataacceleration services for branch-office or remote offices. In oneembodiment, the appliance 205 includes optimization of Wide Area FileServices (WAFS). In another embodiment, the appliance 205 acceleratesthe delivery of files, such as via the Common Internet File System(CIFS) protocol. In other embodiments, the appliance 205 providescaching in memory and/or storage to accelerate delivery of applicationsand data. In one embodiment, the appliance 205 provides compression ofnetwork traffic at any level of the network stack or at any protocol ornetwork layer. In another embodiment, the appliance 205 providestransport layer protocol optimizations, flow control, performanceenhancements or modifications and/or management to accelerate deliveryof applications and data over a WAN connection. For example, in oneembodiment, the appliance 205 provides Transport Control Protocol (TCP)optimizations. In other embodiments, the appliance 205 providesoptimizations, flow control, performance enhancements or modificationsand/or management for any session or application layer protocol.

In another embodiment, the appliance 205 encoded any type and form ofdata or information into custom or standard TCP and/or IP header fieldsor option fields of network packet to announce presence, functionalityor capability to another appliance 205′. In another embodiment, anappliance 205′ may communicate with another appliance 205′ using dataencoded in both TCP and/or IP header fields or options. For example, theappliance may use TCP option(s) or IP header fields or options tocommunicate one or more parameters to be used by the appliances 205,205′ in performing functionality, such as WAN acceleration, or forworking in conjunction with each other.

In some embodiments, the appliance 200 preserves any of the informationencoded in TCP and/or IP header and/or option fields communicatedbetween appliances 205 and 205′. For example, the appliance 200 mayterminate a transport layer connection traversing the appliance 200,such as a transport layer connection from between a client and a servertraversing appliances 205 and 205′. In one embodiment, the appliance 200identifies and preserves any encoded information in a transport layerpacket transmitted by a first appliance 205 via a first transport layerconnection and communicates a transport layer packet with the encodedinformation to a second appliance 205′ via a second transport layerconnection.

Referring now to FIG. 1D, a network environment for delivering and/oroperating a computing environment on a client 102 is depicted. In someembodiments, a server 106 includes an application delivery system 190for delivering a computing environment or an application and/or datafile to one or more clients 102. In brief overview, a client 10 is incommunication with a server 106 via network 104, 104′ and appliance 200.For example, the client 102 may reside in a remote office of a company,e.g., a branch office, and the server 106 may reside at a corporate datacenter. The client 102 comprises a client agent 120, and a computingenvironment 15. The computing environment 15 may execute or operate anapplication that accesses, processes or uses a data file. The computingenvironment 15, application and/or data file may be delivered via theappliance 200 and/or the server 106.

In some embodiments, the appliance 200 accelerates delivery of acomputing environment 15, or any portion thereof, to a client 102. Inone embodiment, the appliance 200 accelerates the delivery of thecomputing environment 15 by the application delivery system 190. Forexample, the embodiments described herein may be used to acceleratedelivery of a streaming application and data file processable by theapplication from a central corporate data center to a remote userlocation, such as a branch office of the company. In another embodiment,the appliance 200 accelerates transport layer traffic between a client102 and a server 106. The appliance 200 may provide accelerationtechniques for accelerating any transport layer payload from a server106 to a client 102, such as: 1) transport layer connection pooling, 2)transport layer connection multiplexing, 3) transport control protocolbuffering, 4) compression and 5) caching. In some embodiments, theappliance 200 provides load balancing of servers 106 in responding torequests from clients 102. In other embodiments, the appliance 200 actsas a proxy or access server to provide access to the one or more servers106. In another embodiment, the appliance 200 provides a secure virtualprivate network connection from a first network 104 of the client 102 tothe second network 104′ of the server 106, such as an SSL VPNconnection. It yet other embodiments, the appliance 200 providesapplication firewall security, control and management of the connectionand communications between a client 102 and a server 106.

In some embodiments, the application delivery management system 190provides application delivery techniques to deliver a computingenvironment to a desktop of a user, remote or otherwise, based on aplurality of execution methods and based on any authentication andauthorization policies applied via a policy engine 195. With thesetechniques, a remote user may obtain a computing environment and accessto server stored applications and data files from any network connecteddevice 100. In one embodiment, the application delivery system 190 mayreside or execute on a server 106. In another embodiment, theapplication delivery system 190 may reside or execute on a plurality ofservers 106 a-106 n. In some embodiments, the application deliverysystem 190 may execute in a server farm 38. In one embodiment, theserver 106 executing the application delivery system 190 may also storeor provide the application and data file. In another embodiment, a firstset of one or more servers 106 may execute the application deliverysystem 190, and a different server 106 n may store or provide theapplication and data file. In some embodiments, each of the applicationdelivery system 190, the application, and data file may reside or belocated on different servers. In yet another embodiment, any portion ofthe application delivery system 190 may reside, execute or be stored onor distributed to the appliance 200, or a plurality of appliances.

The client 102 may include a computing environment 15 for executing anapplication that uses or processes a data file. The client 102 vianetworks 104, 104′ and appliance 200 may request an application and datafile from the server 106. In one embodiment, the appliance 200 mayforward a request from the client 102 to the server 106. For example,the client 102 may not have the application and data file stored oraccessible locally. In response to the request, the application deliverysystem 190 and/or server 106 may deliver the application and data fileto the client 102. For example, in one embodiment, the server 106 maytransmit the application as an application stream to operate incomputing environment 15 on client 102.

In some embodiments, the application delivery system 190 comprises anyportion of the Citrix Workspace Suite™ by Citrix Systems, Inc., such asXenApp® or XenDesktop® and/or any of the Microsoft® Windows TerminalServices manufactured by the Microsoft Corporation. In one embodiment,the application delivery system 190 may deliver one or more applicationsto clients 102 or users via a remote-display protocol or otherwise viaremote-based or server-based computing. In another embodiment, theapplication delivery system 190 may deliver one or more applications toclients or users via steaming of the application.

In one embodiment, the application delivery system 190 includes a policyengine 195 for controlling and managing the access to, selection ofapplication execution methods and the delivery of applications. In someembodiments, the policy engine 195 determines the one or moreapplications a user or client 102 may access. In another embodiment, thepolicy engine 195 determines how the application should be delivered tothe user or client 102, e.g., the method of execution. In someembodiments, the application delivery system 190 provides a plurality ofdelivery techniques from which to select a method of applicationexecution, such as a server-based computing, streaming or delivering theapplication locally to the client 120 for local execution.

In one embodiment, a client 102 requests execution of an applicationprogram and the application delivery system 190 comprising a server 106selects a method of executing the application program. In someembodiments, the server 106 receives credentials from the client 102. Inanother embodiment, the server 106 receives a request for an enumerationof available applications from the client 102. In one embodiment, inresponse to the request or receipt of credentials, the applicationdelivery system 190 enumerates a plurality of application programsavailable to the client 102. The application delivery system 190receives a request to execute an enumerated application. The applicationdelivery system 190 selects one of a predetermined number of methods forexecuting the enumerated application, for example, responsive to apolicy of a policy engine. The application delivery system 190 mayselect a method of execution of the application enabling the client 102to receive application-output data generated by execution of theapplication program on a server 106. The application delivery system 190may select a method of execution of the application enabling the localmachine 10 to execute the application program locally after retrieving aplurality of application files comprising the application. In yetanother embodiment, the application delivery system 190 may select amethod of execution of the application to stream the application via thenetwork 104 to the client 102.

A client 102 may execute, operate or otherwise provide an application,which can be any type and/or form of software, program, or executableinstructions such as any type and/or form of web browser, web-basedclient, client-server application, a thin-client computing client, anActiveX control, or a Java applet, or any other type and/or form ofexecutable instructions capable of executing on client 102. In someembodiments, the application may be a server-based or a remote-basedapplication executed on behalf of the client 102 on a server 106. In oneembodiments the server 106 may display output to the client 102 usingany thin-client or remote-display protocol, such as the IndependentComputing Architecture (ICA) protocol manufactured by Citrix Systems,Inc. of Ft. Lauderdale, Fla. or the Remote Desktop Protocol (RDP)manufactured by the Microsoft Corporation of Redmond, Wash. Theapplication can use any type of protocol and it can be, for example, anHTTP client, an FTP client, an Oscar client, or a Telnet client. Inother embodiments, the application comprises any type of softwarerelated to VoIP communications, such as a soft IP telephone. In furtherembodiments, the application comprises any application related toreal-time data communications, such as applications for streaming videoand/or audio.

In some embodiments, the server 106 or a server farm 38 may be runningone or more applications, such as an application providing a thin-clientcomputing or remote display presentation application. In one embodiment,the server 106 or server farm 38 executes as an application, any portionof the Citrix Workspace Suite™ by Citrix Systems, Inc., such as XenApp®or XenDesktop®, and/or any of the Microsoft® Windows Terminal Servicesmanufactured by the Microsoft Corporation. In one embodiment, theapplication is an ICA client, developed by Citrix Systems, Inc. of FortLauderdale, Fla. In other embodiments, the application includes a RemoteDesktop (RDP) client, developed by Microsoft Corporation of Redmond,Wash. Also, the server 106 may run an application, which for example,may be an application server providing email services such as MicrosoftExchange manufactured by the Microsoft Corporation of Redmond, Wash., aweb or Internet server, or a desktop sharing server, or a collaborationserver. In some embodiments, any of the applications may comprise anytype of hosted service or products, such as GoToMeeting™ provided byCitrix Systems, Inc. of Fort Lauderdale, Fla., WebEx™ provided by CiscoSystems, Inc. of San Jose, Calif., or Microsoft Office Live Meetingprovided by Microsoft Corporation of Redmond, Wash.

Still referring to FIG. 1D, an embodiment of the network environment mayinclude a monitoring server 106A. The monitoring server 106A may includeany type and form performance monitoring service 198. The performancemonitoring service 198 may include monitoring, measurement and/ormanagement software and/or hardware, including data collection,aggregation, analysis, management and reporting. In one embodiment, theperformance monitoring service 198 includes one or more monitoringagents 197. The monitoring agent 197 includes any software, hardware orcombination thereof for performing monitoring, measurement and datacollection activities on a device, such as a client 102, server 106 oran appliance 200, 205. In some embodiments, the monitoring agent 197includes any type and form of script, such as Visual Basic script, orJavascript. In one embodiment, the monitoring agent 197 executestransparently to any application and/or user of the device. In someembodiments, the monitoring agent 197 is installed and operatedunobtrusively to the application or client. In yet another embodiment,the monitoring agent 197 is installed and operated without anyinstrumentation for the application or device.

In some embodiments, the monitoring agent 197 monitors, measures andcollects data on a predetermined frequency. In other embodiments, themonitoring agent 197 monitors, measures and collects data based upondetection of any type and form of event. For example, the monitoringagent 197 may collect data upon detection of a request for a web page orreceipt of an HTTP response. In another example, the monitoring agent197 may collect data upon detection of any user input events, such as amouse click. The monitoring agent 197 may report or provide anymonitored, measured or collected data to the monitoring service 198. Inone embodiment, the monitoring agent 197 transmits information to themonitoring service 198 according to a schedule or a predeterminedfrequency. In another embodiment, the monitoring agent 197 transmitsinformation to the monitoring service 198 upon detection of an event.

In some embodiments, the monitoring service 198 and/or monitoring agent197 performs monitoring and performance measurement of any networkresource or network infrastructure element, such as a client, server,server farm, appliance 200, appliance 205, or network connection. In oneembodiment, the monitoring service 198 and/or monitoring agent 197performs monitoring and performance measurement of any transport layerconnection, such as a TCP or UDP connection. In another embodiment, themonitoring service 198 and/or monitoring agent 197 monitors and measuresnetwork latency. In yet one embodiment, the monitoring service 198and/or monitoring agent 197 monitors and measures bandwidth utilization.

In other embodiments, the monitoring service 198 and/or monitoring agent197 monitors and measures end-user response times. In some embodiments,the monitoring service 198 performs monitoring and performancemeasurement of an application. In another embodiment, the monitoringservice 198 and/or monitoring agent 197 performs monitoring andperformance measurement of any session or connection to the application.In one embodiment, the monitoring service 198 and/or monitoring agent197 monitors and measures performance of a browser. In anotherembodiment, the monitoring service 198 and/or monitoring agent 197monitors and measures performance of HTTP based transactions. In someembodiments, the monitoring service 198 and/or monitoring agent 197monitors and measures performance of a Voice over IP (VoIP) applicationor session. In other embodiments, the monitoring service 198 and/ormonitoring agent 197 monitors and measures performance of a remotedisplay protocol application, such as an ICA client or RDP client. Inyet another embodiment, the monitoring service 198 and/or monitoringagent 197 monitors and measures performance of any type and form ofstreaming media. In still a further embodiment, the monitoring service198 and/or monitoring agent 197 monitors and measures performance of ahosted application or a Software-As-A-Service (SaaS) delivery model.

In some embodiments, the monitoring service 198 and/or monitoring agent197 performs monitoring and performance measurement of one or moretransactions, requests or responses related to application. In otherembodiments, the monitoring service 198 and/or monitoring agent 197monitors and measures any portion of an application layer stack, such asany .NET or J2EE calls. In one embodiment, the monitoring service 198and/or monitoring agent 197 monitors and measures database or SQLtransactions. In yet another embodiment, the monitoring service 198and/or monitoring agent 197 monitors and measures any method, functionor application programming interface (API) call.

In one embodiment, the monitoring service 198 and/or monitoring agent197 performs monitoring and performance measurement of a delivery ofapplication and/or data from a server to a client via one or moreappliances, such as appliance 200 and/or appliance 205. In someembodiments, the monitoring service 198 and/or monitoring agent 197monitors and measures performance of delivery of a virtualizedapplication. In other embodiments, the monitoring service 198 and/ormonitoring agent 197 monitors and measures performance of delivery of astreaming application. In another embodiment, the monitoring service 198and/or monitoring agent 197 monitors and measures performance ofdelivery of a desktop application to a client and/or the execution ofthe desktop application on the client. In another embodiment, themonitoring service 198 and/or monitoring agent 197 monitors and measuresperformance of a client/server application.

In one embodiment, the monitoring service 198 and/or monitoring agent197 is designed and constructed to provide application performancemanagement for the application delivery system 190. For example, themonitoring service 198 and/or monitoring agent 197 may monitor, measureand manage the performance of the delivery of applications via theCitrix Presentation Server. In this example, the monitoring service 198and/or monitoring agent 197 monitors individual ICA sessions. Themonitoring service 198 and/or monitoring agent 197 may measure the totaland per session system resource usage, as well as application andnetworking performance. The monitoring service 198 and/or monitoringagent 197 may identify the active servers for a given user and/or usersession. In some embodiments, the monitoring service 198 and/ormonitoring agent 197 monitors back-end connections between theapplication delivery system 190 and an application and/or databaseserver. The monitoring service 198 and/or monitoring agent 197 maymeasure network latency, delay and volume per user-session or ICAsession.

In some embodiments, the monitoring service 198 and/or monitoring agent197 measures and monitors memory usage for the application deliverysystem 190, such as total memory usage, per user session and/or perprocess. In other embodiments, the monitoring service 198 and/ormonitoring agent 197 measures and monitors CPU usage the applicationdelivery system 190, such as total CPU usage, per user session and/orper process. In another embodiments, the monitoring service 198 and/ormonitoring agent 197 measures and monitors the time required to log-into an application, a server, or the application delivery system, such asCitrix Presentation Server. In one embodiment, the monitoring service198 and/or monitoring agent 197 measures and monitors the duration auser is logged into an application, a server, or the applicationdelivery system 190. In some embodiments, the monitoring service 198and/or monitoring agent 197 measures and monitors active and inactivesession counts for an application, server or application delivery systemsession. In yet another embodiment, the monitoring service 198 and/ormonitoring agent 197 measures and monitors user session latency.

In yet further embodiments, the monitoring service 198 and/or monitoringagent 197 measures and monitors measures and monitors any type and formof server metrics. In one embodiment, the monitoring service 198 and/ormonitoring agent 197 measures and monitors metrics related to systemmemory, CPU usage, and disk storage. In another embodiment, themonitoring service 198 and/or monitoring agent 197 measures and monitorsmetrics related to page faults, such as page faults per second. In otherembodiments, the monitoring service 198 and/or monitoring agent 197measures and monitors round-trip time metrics. In yet anotherembodiment, the monitoring service 198 and/or monitoring agent 197measures and monitors metrics related to application crashes, errorsand/or hangs.

In some embodiments, the monitoring service 198 and monitoring agent 198includes any of the product embodiments referred to as EdgeSightmanufactured by Citrix Systems, Inc. of Ft. Lauderdale, Fla. In anotherembodiment, the performance monitoring service 198 and/or monitoringagent 198 includes any portion of the product embodiments referred to asthe TrueView product suite manufactured by the Symphoniq Corporation ofPalo Alto, Calif. In one embodiment, the performance monitoring service198 and/or monitoring agent 198 includes any portion of the productembodiments referred to as the TeaLeaf CX product suite manufactured bythe TeaLeaf Technology Inc. of San Francisco, Calif. In otherembodiments, the performance monitoring service 198 and/or monitoringagent 198 includes any portion of the business service managementproducts, such as the BMC Performance Manager and Patrol products,manufactured by BMC Software, Inc. of Houston, Tex.

The client 102, server 106, and appliance 200 may be deployed as and/orexecuted on any type and form of computing device, such as a computer,network device or appliance capable of communicating on any type andform of network and performing the operations described herein. FIGS. 1Eand 1F depict block diagrams of a computing device 100 useful forpracticing an embodiment of the client 102, server 106 or appliance 200.As shown in FIGS. 1E and 1F, each computing device 100 includes acentral processing unit 101, and a main memory unit 122. As shown inFIG. 1E, a computing device 100 may include a visual display device 124,a keyboard 126 and/or a pointing device 127, such as a mouse. Eachcomputing device 100 may also include additional optional elements, suchas one or more input/output devices 130 a-130 b (generally referred tousing reference numeral 130), and a cache memory 140 in communicationwith the central processing unit 101.

The central processing unit 101 is any logic circuitry that responds toand processes instructions fetched from the main memory unit 122. Inmany embodiments, the central processing unit is provided by amicroprocessor unit, such as: those manufactured by Intel Corporation ofMountain View, Calif.; those manufactured by Motorola Corporation ofSchaumburg, Ill.; those manufactured by Transmeta Corporation of SantaClara, Calif.; the RS/6000 processor, those manufactured byInternational Business Machines of White Plains, N.Y.; or thosemanufactured by Advanced Micro Devices of Sunnyvale, Calif. Thecomputing device 100 may be based on any of these processors, or anyother processor capable of operating as described herein.

Main memory unit 122 may be one or more memory chips capable of storingdata and allowing any storage location to be directly accessed by themicroprocessor 101, such as Static random access memory (SRAM), BurstSRAM or SynchBurst SRAM (BSRAM), Dynamic random access memory (DRAM),Fast Page Mode DRAM (FPM DRAM), Enhanced DRAM (EDRAM), Extended DataOutput RAM (EDO RAM), Extended Data Output DRAM (EDO DRAM), BurstExtended Data Output DRAM (BEDO DRAM), Enhanced DRAM (EDRAM),synchronous DRAM (SDRAM), JEDEC SRAM, PC100 SDRAM, Double Data RateSDRAM (DDR SDRAM), Enhanced SDRAM (ESDRAM), SyncLink DRAM (SLDRAM),Direct Rambus DRAM (DRDRAM), or Ferroelectric RAM (FRAM). The mainmemory 122 may be based on any of the above described memory chips, orany other available memory chips capable of operating as describedherein. In the embodiment shown in FIG. 1E, the processor 101communicates with main memory 122 via a system bus 150 (described inmore detail below). FIG. 1F depicts an embodiment of a computing device100 in which the processor communicates directly with main memory 122via a memory port 103. For example, in FIG. 1F the main memory 122 maybe DRDRAM.

FIG. 1F depicts an embodiment in which the main processor 101communicates directly with cache memory 140 via a secondary bus,sometimes referred to as a backside bus. In other embodiments, the mainprocessor 101 communicates with cache memory 140 using the system bus150. Cache memory 140 typically has a faster response time than mainmemory 122 and is typically provided by SRAM, BSRAM, or EDRAM. In theembodiment shown in FIG. 1F, the processor 101 communicates with variousI/O devices 130 via a local system bus 150. Various busses may be usedto connect the central processing unit 101 to any of the I/O devices130, including a VESA VL bus, an ISA bus, an EISA bus, a MicroChannelArchitecture (MCA) bus, a PCI bus, a PCI-X bus, a PCI-Express bus, or aNuBus. For embodiments in which the I/O device is a video display 124,the processor 101 may use an Advanced Graphics Port (AGP) to communicatewith the display 124. FIG. 1F depicts an embodiment of a computer 100 inwhich the main processor 101 communicates directly with I/O device 130 bvia HyperTransport, Rapid I/O, or InfiniBand. FIG. 1F also depicts anembodiment in which local busses and direct communication are mixed: theprocessor 101 communicates with I/O device 130 b using a localinterconnect bus while communicating with I/O device 130 a directly.

The computing device 100 may support any suitable installation device116, such as a floppy disk drive for receiving floppy disks such as3.5-inch, 5.25-inch disks or ZIP disks, a CD-ROM drive, a CD-R/RW drive,a DVD-ROM drive, tape drives of various formats, USB device, hard-driveor any other device suitable for installing software and programs suchas any client agent 120, or portion thereof. The computing device 100may further comprise a storage device 128, such as one or more hard diskdrives or redundant arrays of independent disks, for storing anoperating system and other related software, and for storing applicationsoftware programs such as any program related to the client agent 120.Optionally, any of the installation devices 116 could also be used asthe storage device 128. Additionally, the operating system and thesoftware can be run from a bootable medium, for example, a bootable CD,such as KNOPPIX®, a bootable CD for GNU/Linux that is available as aGNU/Linux distribution from knoppix.net.

Furthermore, the computing device 100 may include a network interface118 to interface to a Local Area Network (LAN), Wide Area Network (WAN)or the Internet through a variety of connections including, but notlimited to, standard telephone lines, LAN or WAN links (e.g., 802.11,T1, T3, 56 kb, X.25), broadband connections (e.g., ISDN, Frame Relay,ATM), wireless connections, or some combination of any or all of theabove. The network interface 118 may comprise a built-in networkadapter, network interface card, PCMCIA network card, card bus networkadapter, wireless network adapter, USB network adapter, modem or anyother device suitable for interfacing the computing device 100 to anytype of network capable of communication and performing the operationsdescribed herein.

A wide variety of I/O devices 130 a-130 n may be present in thecomputing device 100. Input devices include keyboards, mice, trackpads,trackballs, microphones, and drawing tablets. Output devices includevideo displays, speakers, inkjet printers, laser printers, anddye-sublimation printers. The I/O devices 130 may be controlled by anI/O controller 123 as shown in FIG. 1E. The I/O controller may controlone or more I/O devices such as a keyboard 126 and a pointing device127, e.g., a mouse or optical pen. Furthermore, an I/O device may alsoprovide storage 128 and/or an installation medium 116 for the computingdevice 100. In still other embodiments, the computing device 100 mayprovide USB connections to receive handheld USB storage devices such asthe USB Flash Drive line of devices manufactured by Twintech Industry,Inc. of Los Alamitos, Calif.

In some embodiments, the computing device 100 may comprise or beconnected to multiple display devices 124 a-124 n, which each may be ofthe same or different type and/or form. As such, any of the I/O devices130 a-130 n and/or the I/O controller 123 may comprise any type and/orform of suitable hardware, software, or combination of hardware andsoftware to support, enable or provide for the connection and use ofmultiple display devices 124 a-124 n by the computing device 100. Forexample, the computing device 100 may include any type and/or form ofvideo adapter, video card, driver, and/or library to interface,communicate, connect or otherwise use the display devices 124 a-124 n.In one embodiment, a video adapter may comprise multiple connectors tointerface to multiple display devices 124 a-124 n. In other embodiments,the computing device 100 may include multiple video adapters, with eachvideo adapter connected to one or more of the display devices 124 a-124n. In some embodiments, any portion of the operating system of thecomputing device 100 may be configured for using multiple displays 124a-124 n. In other embodiments, one or more of the display devices 124a-124 n may be provided by one or more other computing devices, such ascomputing devices 100 a and 100 b connected to the computing device 100,for example, via a network. These embodiments may include any type ofsoftware designed and constructed to use another computer's displaydevice as a second display device 124 a for the computing device 100.One ordinarily skilled in the art will recognize and appreciate thevarious ways and embodiments that a computing device 100 may beconfigured to have multiple display devices 124 a-124 n.

In further embodiments, an I/O device 130 may be a bridge 170 betweenthe system bus 150 and an external communication bus, such as a USB bus,an Apple Desktop Bus, an RS-232 serial connection, a SCSI bus, aFireWire bus, a FireWire 800 bus, an Ethernet bus, an AppleTalk bus, aGigabit Ethernet bus, an Asynchronous Transfer Mode bus, a HIPPI bus, aSuper HIPPI bus, a SerialPlus bus, a SCI/LAMP bus, a FibreChannel bus,or a Serial Attached small computer system interface bus.

A computing device 100 of the sort depicted in FIGS. 1E and 1F typicallyoperate under the control of operating systems, which control schedulingof tasks and access to system resources. The computing device 100 can berunning any operating system such as any of the versions of theMicrosoft® Windows operating systems, the different releases of the Unixand Linux operating systems, any version of the Mac OS® for Macintoshcomputers, any embedded operating system, any real-time operatingsystem, any open source operating system, any proprietary operatingsystem, any operating systems for mobile computing devices, or any otheroperating system capable of running on the computing device andperforming the operations described herein. Typical operating systemsinclude: WINDOWS 3.x, WINDOWS 95, WINDOWS 98, WINDOWS 2000, WINDOWS NT3.51, WINDOWS NT 4.0, WINDOWS CE, and WINDOWS XP, all of which aremanufactured by Microsoft Corporation of Redmond, Wash.; MacOS,manufactured by Apple Computer of Cupertino, Calif.; OS/2, manufacturedby International Business Machines of Armonk, N.Y.; and Linux, afreely-available operating system distributed by Caldera Corp. of SaltLake City, Utah, or any type and/or form of a UNIX operating system,among others.

In other embodiments, the computing device 100 may have differentprocessors, operating systems, and input devices consistent with thedevice. For example, in one embodiment the computer 100 is a Treo 180,270, 1060, 600 or 650 smart phone manufactured by Palm, Inc. In thisembodiment, the Treo smart phone is operated under the control of thePalmOS operating system and includes a stylus input device as well as afive-way navigator device. Moreover, the computing device 100 can be anyworkstation, desktop computer, laptop or notebook computer, server,handheld computer, mobile telephone, any other computer, or other formof computing or telecommunications device that is capable ofcommunication and that has sufficient processor power and memorycapacity to perform the operations described herein.

As shown in FIG. 1G, the computing device 100 may comprise multipleprocessors and may provide functionality for simultaneous execution ofinstructions or for simultaneous execution of one instruction on morethan one piece of data. In some embodiments, the computing device 100may comprise a parallel processor with one or more cores. In one ofthese embodiments, the computing device 100 is a shared memory paralleldevice, with multiple processors and/or multiple processor cores,accessing all available memory as a single global address space. Inanother of these embodiments, the computing device 100 is a distributedmemory parallel device with multiple processors each accessing localmemory only. In still another of these embodiments, the computing device100 has both some memory which is shared and some memory which can onlybe accessed by particular processors or subsets of processors. In stilleven another of these embodiments, the computing device 100, such as amulti-core microprocessor, combines two or more independent processorsinto a single package, often a single integrated circuit (IC). In yetanother of these embodiments, the computing device 100 includes a chiphaving a CELL BROADBAND ENGINE architecture and including a Powerprocessor element and a plurality of synergistic processing elements,the Power processor element and the plurality of synergistic processingelements linked together by an internal high speed bus, which may bereferred to as an element interconnect bus.

In some embodiments, the processors provide functionality for executionof a single instruction simultaneously on multiple pieces of data(SIMD). In other embodiments, the processors provide functionality forexecution of multiple instructions simultaneously on multiple pieces ofdata (MIMD). In still other embodiments, the processor may use anycombination of SIMD and MIMD cores in a single device.

In some embodiments, the computing device 100 may comprise a graphicsprocessing unit. In one of these embodiments depicted in FIG. 1H, thecomputing device 100 includes at least one central processing unit 101and at least one graphics processing unit. In another of theseembodiments, the computing device 100 includes at least one parallelprocessing unit and at least one graphics processing unit. In stillanother of these embodiments, the computing device 100 includes aplurality of processing units of any type, one of the plurality ofprocessing units comprising a graphics processing unit.

In some embodiments, a first computing device 100 a executes anapplication on behalf of a user of a client computing device 100 b. Inother embodiments, a computing device 100 a executes a virtual machine,which provides an execution session within which applications execute onbehalf of a user or a client computing devices 100 b. In one of theseembodiments, the execution session is a hosted desktop session. Inanother of these embodiments, the computing device 100 executes aterminal services session. The terminal services session may provide ahosted desktop environment. In still another of these embodiments, theexecution session provides access to a computing environment, which maycomprise one or more of: an application, a plurality of applications, adesktop application, and a desktop session in which one or moreapplications may execute.

B. Appliance Architecture

FIG. 2A illustrates an example embodiment of the appliance 200. Thearchitecture of the appliance 200 in FIG. 2A is provided by way ofillustration only and is not intended to be limiting. As shown in FIG.2, appliance 200 comprises a hardware layer 206 and a software layerdivided into a user space 202 and a kernel space 204.

Hardware layer 206 provides the hardware elements upon which programsand services within kernel space 204 and user space 202 are executed.Hardware layer 206 also provides the structures and elements which allowprograms and services within kernel space 204 and user space 202 tocommunicate data both internally and externally with respect toappliance 200. As shown in FIG. 2, the hardware layer 206 includes aprocessing unit 262 for executing software programs and services, amemory 264 for storing software and data, network ports 266 fortransmitting and receiving data over a network, and an encryptionprocessor 260 for performing functions related to Secure Sockets Layerprocessing of data transmitted and received over the network. In someembodiments, the central processing unit 262 may perform the functionsof the encryption processor 260 in a single processor. Additionally, thehardware layer 206 may comprise multiple processors for each of theprocessing unit 262 and the encryption processor 260. The processor 262may include any of the processors 101 described above in connection withFIGS. 1E and 1F. For example, in one embodiment, the appliance 200comprises a first processor 262 and a second processor 262′. In otherembodiments, the processor 262 or 262′ comprises a multi-core processor.

Although the hardware layer 206 of appliance 200 is generallyillustrated with an encryption processor 260, processor 260 may be aprocessor for performing functions related to any encryption protocol,such as the Secure Socket Layer (SSL) or Transport Layer Security (TLS)protocol. In some embodiments, the processor 260 may be a generalpurpose processor (GPP), and in further embodiments, may have executableinstructions for performing processing of any security related protocol.

Although the hardware layer 206 of appliance 200 is illustrated withcertain elements in FIG. 2, the hardware portions or components ofappliance 200 may comprise any type and form of elements, hardware orsoftware, of a computing device, such as the computing device 100illustrated and discussed herein in conjunction with FIGS. 1E and 1F. Insome embodiments, the appliance 200 may comprise a server, gateway,router, switch, bridge or other type of computing or network device, andhave any hardware and/or software elements associated therewith.

The operating system of appliance 200 allocates, manages, or otherwisesegregates the available system memory into kernel space 204 and userspace 204. In example software architecture 200, the operating systemmay be any type and/or form of UNIX operating system although theinvention is not so limited. As such, the appliance 200 can be runningany operating system such as any of the versions of the Microsoft®Windows operating systems, the different releases of the Unix and Linuxoperating systems, any version of the Mac OS® for Macintosh computers,any embedded operating system, any network operating system, anyreal-time operating system, any open source operating system, anyproprietary operating system, any operating systems for mobile computingdevices or network devices, or any other operating system capable ofrunning on the appliance 200 and performing the operations describedherein.

The kernel space 204 is reserved for running the kernel 230, includingany device drivers, kernel extensions or other kernel related software.As known to those skilled in the art, the kernel 230 is the core of theoperating system, and provides access, control, and management ofresources and hardware-related elements of the application 104. Inaccordance with an embodiment of the appliance 200, the kernel space 204also includes a number of network services or processes working inconjunction with a cache manager 232, sometimes also referred to as theintegrated cache, the benefits of which are described in detail furtherherein. Additionally, the embodiment of the kernel 230 will depend onthe embodiment of the operating system installed, configured, orotherwise used by the device 200.

In one embodiment, the device 200 comprises one network stack 267, suchas a TCP/IP based stack, for communicating with the client 102 and/orthe server 106. In one embodiment, the network stack 267 is used tocommunicate with a first network, such as network 108, and a secondnetwork 110. In some embodiments, the device 200 terminates a firsttransport layer connection, such as a TCP connection of a client 102,and establishes a second transport layer connection to a server 106 foruse by the client 102, e.g., the second transport layer connection isterminated at the appliance 200 and the server 106. The first and secondtransport layer connections may be established via a single networkstack 267. In other embodiments, the device 200 may comprise multiplenetwork stacks, for example 267 and 267′, and the first transport layerconnection may be established or terminated at one network stack 267,and the second transport layer connection on the second network stack267′. For example, one network stack may be for receiving andtransmitting network packet on a first network, and another networkstack for receiving and transmitting network packets on a secondnetwork. In one embodiment, the network stack 267 comprises a buffer 243for queuing one or more network packets for transmission by theappliance 200.

As shown in FIG. 2, the kernel space 204 includes the cache manager 232,a high-speed layer 2-7 integrated packet engine 240, an encryptionengine 234, a policy engine 236 and multi-protocol compression logic238. Running these components or processes 232, 240, 234, 236 and 238 inkernel space 204 or kernel mode instead of the user space 202 improvesthe performance of each of these components, alone and in combination.Kernel operation means that these components or processes 232, 240, 234,236 and 238 run in the core address space of the operating system of thedevice 200. For example, running the encryption engine 234 in kernelmode improves encryption performance by moving encryption and decryptionoperations to the kernel, thereby reducing the number of transitionsbetween the memory space or a kernel thread in kernel mode and thememory space or a thread in user mode. For example, data obtained inkernel mode may not need to be passed or copied to a process or threadrunning in user mode, such as from a kernel level data structure to auser level data structure. In another aspect, the number of contextswitches between kernel mode and user mode are also reduced.Additionally, synchronization of and communications between any of thecomponents or processes 232, 240, 235, 236 and 238 can be performed moreefficiently in the kernel space 204.

In some embodiments, any portion of the components 232, 240, 234, 236and 238 may run or operate in the kernel space 204, while other portionsof these components 232, 240, 234, 236 and 238 may run or operate inuser space 202. In one embodiment, the appliance 200 uses a kernel-leveldata structure providing access to any portion of one or more networkpackets, for example, a network packet comprising a request from aclient 102 or a response from a server 106. In some embodiments, thekernel-level data structure may be obtained by the packet engine 240 viaa transport layer driver interface or filter to the network stack 267.The kernel-level data structure may comprise any interface and/or dataaccessible via the kernel space 204 related to the network stack 267,network traffic or packets received or transmitted by the network stack267. In other embodiments, the kernel-level data structure may be usedby any of the components or processes 232, 240, 234, 236 and 238 toperform the desired operation of the component or process. In oneembodiment, a component 232, 240, 234, 236 and 238 is running in kernelmode 204 when using the kernel-level data structure, while in anotherembodiment, the component 232, 240, 234, 236 and 238 is running in usermode when using the kernel-level data structure. In some embodiments,the kernel-level data structure may be copied or passed to a secondkernel-level data structure, or any desired user-level data structure.

The cache manager 232 may comprise software, hardware or any combinationof software and hardware to provide cache access, control and managementof any type and form of content, such as objects or dynamicallygenerated objects served by the originating servers 106. The data,objects or content processed and stored by the cache manager 232 maycomprise data in any format, such as a markup language, or communicatedvia any protocol. In some embodiments, the cache manager 232 duplicatesoriginal data stored elsewhere or data previously computed, generated ortransmitted, in which the original data may require longer access timeto fetch, compute or otherwise obtain relative to reading a cache memoryelement. Once the data is stored in the cache memory element, future usecan be made by accessing the cached copy rather than refetching orrecomputing the original data, thereby reducing the access time. In someembodiments, the cache memory element may comprise a data object inmemory 264 of device 200. In other embodiments, the cache memory elementmay comprise memory having a faster access time than memory 264. Inanother embodiment, the cache memory element may comprise any type andform of storage element of the device 200, such as a portion of a harddisk. In some embodiments, the processing unit 262 may provide cachememory for use by the cache manager 232. In yet further embodiments, thecache manager 232 may use any portion and combination of memory,storage, or the processing unit for caching data, objects, and othercontent.

Furthermore, the cache manager 232 includes any logic, functions, rules,or operations to perform any embodiments of the techniques of theappliance 200 described herein. For example, the cache manager 232includes logic or functionality to invalidate objects based on theexpiration of an invalidation time period or upon receipt of aninvalidation command from a client 102 or server 106. In someembodiments, the cache manager 232 may operate as a program, service,process or task executing in the kernel space 204, and in otherembodiments, in the user space 202. In one embodiment, a first portionof the cache manager 232 executes in the user space 202 while a secondportion executes in the kernel space 204. In some embodiments, the cachemanager 232 can comprise any type of general purpose processor (GPP), orany other type of integrated circuit, such as a Field Programmable GateArray (FPGA), Programmable Logic Device (PLD), or Application SpecificIntegrated Circuit (ASIC).

The policy engine 236 may include, for example, an intelligentstatistical engine or other programmable application(s). In oneembodiment, the policy engine 236 provides a configuration mechanism toallow a user to identify, specify, define or configure a caching policy.Policy engine 236, in some embodiments, also has access to memory tosupport data structures such as lookup tables or hash tables to enableuser-selected caching policy decisions. In other embodiments, the policyengine 236 may comprise any logic, rules, functions or operations todetermine and provide access, control and management of objects, data orcontent being cached by the appliance 200 in addition to access, controland management of security, network traffic, network access, compressionor any other function or operation performed by the appliance 200.Further examples of specific caching policies are further describedherein.

The encryption engine 234 comprises any logic, business rules, functionsor operations for handling the processing of any security relatedprotocol, such as SSL or TLS, or any function related thereto. Forexample, the encryption engine 234 encrypts and decrypts networkpackets, or any portion thereof, communicated via the appliance 200. Theencryption engine 234 may also setup or establish SSL or TLS connectionson behalf of the client 102 a-102 n, server 106 a-106 n, or appliance200. As such, the encryption engine 234 provides offloading andacceleration of SSL processing. In one embodiment, the encryption engine234 uses a tunneling protocol to provide a virtual private networkbetween a client 102 a-102 n and a server 106 a-106 n. In someembodiments, the encryption engine 234 is in communication with theEncryption processor 260. In other embodiments, the encryption engine234 comprises executable instructions running on the Encryptionprocessor 260.

The multi-protocol compression engine 238 comprises any logic, businessrules, function or operations for compressing one or more protocols of anetwork packet, such as any of the protocols used by the network stack267 of the device 200. In one embodiment, multi-protocol compressionengine 238 compresses bi-directionally between clients 102 a-102 n andservers 106 a-106 n any TCP/IP based protocol, including MessagingApplication Programming Interface (MAPI) (email), File Transfer Protocol(FTP), HyperText Transfer Protocol (HTTP), Common Internet File System(CIFS) protocol (file transfer), Independent Computing Architecture(ICA) protocol, Remote Desktop Protocol (RDP), Wireless ApplicationProtocol (WAP), Mobile IP protocol, and Voice Over IP (VoIP) protocol.In other embodiments, multi-protocol compression engine 238 providescompression of Hypertext Markup Language (HTML) based protocols and insome embodiments, provides compression of any markup languages, such asthe Extensible Markup Language (XML). In one embodiment, themulti-protocol compression engine 238 provides compression of anyhigh-performance protocol, such as any protocol designed for appliance200 to appliance 200 communications. In another embodiment, themulti-protocol compression engine 238 compresses any payload of or anycommunication using a modified transport control protocol, such asTransaction TCP (T/TCP), TCP with selection acknowledgements (TCP-SACK),TCP with large windows (TCP-LW), a congestion prediction protocol suchas the TCP-Vegas protocol, and a TCP spoofing protocol.

As such, the multi-protocol compression engine 238 acceleratesperformance for users accessing applications via desktop clients, e.g.,Microsoft Outlook and non-Web thin clients, such as any client launchedby popular enterprise applications like Oracle, SAP and Siebel, and evenmobile clients, such as the Pocket PC. In some embodiments, themulti-protocol compression engine 238 by executing in the kernel mode204 and integrating with packet processing engine 240 accessing thenetwork stack 267 is able to compress any of the protocols carried bythe TCP/IP protocol, such as any application layer protocol.

High speed layer 2-7 integrated packet engine 240, also generallyreferred to as a packet processing engine or packet engine, isresponsible for managing the kernel-level processing of packets receivedand transmitted by appliance 200 via network ports 266. The high speedlayer 2-7 integrated packet engine 240 may comprise a buffer for queuingone or more network packets during processing, such as for receipt of anetwork packet or transmission of a network packet. Additionally, thehigh speed layer 2-7 integrated packet engine 240 is in communicationwith one or more network stacks 267 to send and receive network packetsvia network ports 266. The high speed layer 2-7 integrated packet engine240 works in conjunction with encryption engine 234, cache manager 232,policy engine 236 and multi-protocol compression logic 238. Inparticular, encryption engine 234 is configured to perform SSLprocessing of packets, policy engine 236 is configured to performfunctions related to traffic management such as request-level contentswitching and request-level cache redirection, and multi-protocolcompression logic 238 is configured to perform functions related tocompression and decompression of data.

The high speed layer 2-7 integrated packet engine 240 includes a packetprocessing timer 242. In one embodiment, the packet processing timer 242provides one or more time intervals to trigger the processing ofincoming, i.e., received, or outgoing, i.e., transmitted, networkpackets. In some embodiments, the high speed layer 2-7 integrated packetengine 240 processes network packets responsive to the timer 242. Thepacket processing timer 242 provides any type and form of signal to thepacket engine 240 to notify, trigger, or communicate a time relatedevent, interval or occurrence. In many embodiments, the packetprocessing timer 242 operates in the order of milliseconds, such as forexample 100 ms, 50 ms or 25 ms. For example, in some embodiments, thepacket processing timer 242 provides time intervals or otherwise causesa network packet to be processed by the high speed layer 2-7 integratedpacket engine 240 at a 10 ms time interval, while in other embodiments,at a 5 ms time interval, and still yet in further embodiments, as shortas a 3, 2, or 1 ms time interval. The high speed layer 2-7 integratedpacket engine 240 may be interfaced, integrated or in communication withthe encryption engine 234, cache manager 232, policy engine 236 andmulti-protocol compression engine 238 during operation. As such, any ofthe logic, functions, or operations of the encryption engine 234, cachemanager 232, policy engine 236 and multi-protocol compression logic 238may be performed responsive to the packet processing timer 242 and/orthe packet engine 240. Therefore, any of the logic, functions, oroperations of the encryption engine 234, cache manager 232, policyengine 236 and multi-protocol compression logic 238 may be performed atthe granularity of time intervals provided via the packet processingtimer 242, for example, at a time interval of less than or equal to 10ms. For example, in one embodiment, the cache manager 232 may performinvalidation of any cached objects responsive to the high speed layer2-7 integrated packet engine 240 and/or the packet processing timer 242.In another embodiment, the expiry or invalidation time of a cachedobject can be set to the same order of granularity as the time intervalof the packet processing timer 242, such as at every 10 ms.

In contrast to kernel space 204, user space 202 is the memory area orportion of the operating system used by user mode applications orprograms otherwise running in user mode. A user mode application may notaccess kernel space 204 directly and uses service calls in order toaccess kernel services. As shown in FIG. 2, user space 202 of appliance200 includes a graphical user interface (GUI) 210, a command lineinterface (CLI) 212, shell services 214, health monitoring program 216,and daemon services 218. GUI 210 and CLI 212 provide a means by which asystem administrator or other user can interact with and control theoperation of appliance 200, such as via the operating system of theappliance 200. The GUI 210 or CLI 212 can comprise code running in userspace 202 or kernel space 204. The GUI 210 may be any type and form ofgraphical user interface and may be presented via text, graphical orotherwise, by any type of program or application, such as a browser. TheCLI 212 may be any type and form of command line or text-basedinterface, such as a command line provided by the operating system. Forexample, the CLI 212 may comprise a shell, which is a tool to enableusers to interact with the operating system. In some embodiments, theCLI 212 may be provided via a bash, csh, tcsh, or ksh type shell. Theshell services 214 comprises the programs, services, tasks, processes orexecutable instructions to support interaction with the appliance 200 oroperating system by a user via the GUI 210 and/or CLI 212.

Health monitoring program 216 is used to monitor, check, report andensure that network systems are functioning properly and that users arereceiving requested content over a network. Health monitoring program216 comprises one or more programs, services, tasks, processes orexecutable instructions to provide logic, rules, functions or operationsfor monitoring any activity of the appliance 200. In some embodiments,the health monitoring program 216 intercepts and inspects any networktraffic passed via the appliance 200. In other embodiments, the healthmonitoring program 216 interfaces by any suitable means and/ormechanisms with one or more of the following: the encryption engine 234,cache manager 232, policy engine 236, multi-protocol compression logic238, packet engine 240, daemon services 218, and shell services 214. Assuch, the health monitoring program 216 may call any applicationprogramming interface (API) to determine a state, status, or health ofany portion of the appliance 200. For example, the health monitoringprogram 216 may ping or send a status inquiry on a periodic basis tocheck if a program, process, service or task is active and currentlyrunning. In another example, the health monitoring program 216 may checkany status, error or history logs provided by any program, process,service or task to determine any condition, status or error with anyportion of the appliance 200.

Daemon services 218 are programs that run continuously or in thebackground and handle periodic service requests received by appliance200. In some embodiments, a daemon service may forward the requests toother programs or processes, such as another daemon service 218 asappropriate. As known to those skilled in the art, a daemon service 218may run unattended to perform continuous or periodic system widefunctions, such as network control, or to perform any desired task. Insome embodiments, one or more daemon services 218 run in the user space202, while in other embodiments, one or more daemon services 218 run inthe kernel space.

Referring now to FIG. 2B, another embodiment of the appliance 200 isdepicted. In brief overview, the appliance 200 provides one or more ofthe following services, functionality or operations: SSL VPNconnectivity 280, switching/load balancing 284, Domain Name Serviceresolution 286, acceleration 288 and an application firewall 290 forcommunications between one or more clients 102 and one or more servers106. Each of the servers 106 may provide one or more network relatedservices 270 a-270 n (referred to as services 270). For example, aserver 106 may provide an http service 270. The appliance 200 comprisesone or more virtual servers or virtual internet protocol servers,referred to as a vServer, VIP server, or just VIP 275 a-275 n (alsoreferred herein as vServer 275). The vServer 275 receives, intercepts orotherwise processes communications between a client 102 and a server 106in accordance with the configuration and operations of the appliance200.

The vServer 275 may comprise software, hardware or any combination ofsoftware and hardware. The vServer 275 may comprise any type and form ofprogram, service, task, process or executable instructions operating inuser mode 202, kernel mode 204 or any combination thereof in theappliance 200. The vServer 275 includes any logic, functions, rules, oroperations to perform any embodiments of the techniques describedherein, such as SSL VPN 280, switching/load balancing 284, Domain NameService resolution 286, acceleration 288 and an application firewall290. In some embodiments, the vServer 275 establishes a connection to aservice 270 of a server 106. The service 275 may comprise any program,application, process, task or set of executable instructions capable ofconnecting to and communicating to the appliance 200, client 102 orvServer 275. For example, the service 275 may comprise a web server,http server, ftp, email or database server. In some embodiments, theservice 270 is a daemon process or network driver for listening,receiving and/or sending communications for an application, such asemail, database or an enterprise application. In some embodiments, theservice 270 may communicate on a specific IP address, or IP address andport.

In some embodiments, the vServer 275 applies one or more policies of thepolicy engine 236 to network communications between the client 102 andserver 106. In one embodiment, the policies are associated with avServer 275. In another embodiment, the policies are based on a user, ora group of users. In yet another embodiment, a policy is global andapplies to one or more vServers 275 a-275 n, and any user or group ofusers communicating via the appliance 200. In some embodiments, thepolicies of the policy engine have conditions upon which the policy isapplied based on any content of the communication, such as internetprotocol address, port, protocol type, header or fields in a packet, orthe context of the communication, such as user, group of the user,vServer 275, transport layer connection, and/or identification orattributes of the client 102 or server 106.

In other embodiments, the appliance 200 communicates or interfaces withthe policy engine 236 to determine authentication and/or authorizationof a remote user or a remote client 102 to access the computingenvironment 15, application, and/or data file from a server 106. Inanother embodiment, the appliance 200 communicates or interfaces withthe policy engine 236 to determine authentication and/or authorizationof a remote user or a remote client 102 to have the application deliverysystem 190 deliver one or more of the computing environment 15,application, and/or data file. In yet another embodiment, the appliance200 establishes a VPN or SSL VPN connection based on the policy engine's236 authentication and/or authorization of a remote user or a remoteclient 102 In one embodiment, the appliance 200 controls the flow ofnetwork traffic and communication sessions based on policies of thepolicy engine 236. For example, the appliance 200 may control the accessto a computing environment 15, application or data file based on thepolicy engine 236.

In some embodiments, the vServer 275 establishes a transport layerconnection, such as a TCP or UDP connection with a client 102 via theclient agent 120. In one embodiment, the vServer 275 listens for andreceives communications from the client 102. In other embodiments, thevServer 275 establishes a transport layer connection, such as a TCP orUDP connection with a client server 106. In one embodiment, the vServer275 establishes the transport layer connection to an internet protocoladdress and port of a server 270 running on the server 106. In anotherembodiment, the vServer 275 associates a first transport layerconnection to a client 102 with a second transport layer connection tothe server 106. In some embodiments, a vServer 275 establishes a pool oftransport layer connections to a server 106 and multiplexes clientrequests via the pooled transport layer connections.

In some embodiments, the appliance 200 provides a SSL VPN connection 280between a client 102 and a server 106. For example, a client 102 on afirst network 102 requests to establish a connection to a server 106 ona second network 104′. In some embodiments, the second network 104′ isnot routable from the first network 104. In other embodiments, theclient 102 is on a public network 104 and the server 106 is on a privatenetwork 104′, such as a corporate network. In one embodiment, the clientagent 120 intercepts communications of the client 102 on the firstnetwork 104, encrypts the communications, and transmits thecommunications via a first transport layer connection to the appliance200. The appliance 200 associates the first transport layer connectionon the first network 104 to a second transport layer connection to theserver 106 on the second network 104. The appliance 200 receives theintercepted communication from the client agent 102, decrypts thecommunications, and transmits the communication to the server 106 on thesecond network 104 via the second transport layer connection. The secondtransport layer connection may be a pooled transport layer connection.As such, the appliance 200 provides an end-to-end secure transport layerconnection for the client 102 between the two networks 104, 104′.

In one embodiment, the appliance 200 hosts an intranet internet protocolor IntranetIP 282 address of the client 102 on the virtual privatenetwork 104. The client 102 has a local network identifier, such as aninternet protocol (IP) address and/or host name on the first network104. When connected to the second network 104′ via the appliance 200,the appliance 200 establishes, assigns or otherwise provides anIntranetIP address 282, which is a network identifier, such as IPaddress and/or host name, for the client 102 on the second network 104′.The appliance 200 listens for and receives on the second or privatenetwork 104′ for any communications directed towards the client 102using the client's established IntranetIP 282. In one embodiment, theappliance 200 acts as or on behalf of the client 102 on the secondprivate network 104. For example, in another embodiment, a vServer 275listens for and responds to communications to the IntranetIP 282 of theclient 102. In some embodiments, if a computing device 100 on the secondnetwork 104′ transmits a request, the appliance 200 processes therequest as if it were the client 102. For example, the appliance 200 mayrespond to a ping to the client's IntranetIP 282. In another example,the appliance may establish a connection, such as a TCP or UDPconnection, with computing device 100 on the second network 104requesting a connection with the client's IntranetIP 282.

In some embodiments, the appliance 200 provides one or more of thefollowing acceleration techniques 288 to communications between theclient 102 and server 106: 1) compression; 2) decompression; 3)Transmission Control Protocol pooling; 4) Transmission Control Protocolmultiplexing; 5) Transmission Control Protocol buffering; and 6)caching.

In one embodiment, the appliance 200 relieves servers 106 of much of theprocessing load caused by repeatedly opening and closing transportlayers connections to clients 102 by opening one or more transport layerconnections with each server 106 and maintaining these connections toallow repeated data accesses by clients via the Internet. This techniqueis referred to herein as “connection pooling”.

In some embodiments, in order to seamlessly splice communications from aclient 102 to a server 106 via a pooled transport layer connection, theappliance 200 translates or multiplexes communications by modifyingsequence number and acknowledgment numbers at the transport layerprotocol level. This is referred to as “connection multiplexing”. Insome embodiments, no application layer protocol interaction is required.For example, in the case of an in-bound packet (that is, a packetreceived from a client 102), the source network address of the packet ischanged to that of an output port of appliance 200, and the destinationnetwork address is changed to that of the intended server. In the caseof an outbound packet (that is, one received from a server 106), thesource network address is changed from that of the server 106 to that ofan output port of appliance 200 and the destination address is changedfrom that of appliance 200 to that of the requesting client 102. Thesequence numbers and acknowledgment numbers of the packet are alsotranslated to sequence numbers and acknowledgement numbers expected bythe client 102 on the appliance's 200 transport layer connection to theclient 102. In some embodiments, the packet checksum of the transportlayer protocol is recalculated to account for these translations.

In another embodiment, the appliance 200 provides switching orload-balancing functionality 284 for communications between the client102 and server 106. In some embodiments, the appliance 200 distributestraffic and directs client requests to a server 106 based on layer 4 orapplication-layer request data. In one embodiment, although the networklayer or layer 2 of the network packet identifies a destination server106, the appliance 200 determines the server 106 to distribute thenetwork packet by application information and data carried as payload ofthe transport layer packet. In one embodiment, the health monitoringprograms 216 of the appliance 200 monitor the health of servers todetermine the server 106 for which to distribute a client's request. Insome embodiments, if the appliance 200 detects a server 106 is notavailable or has a load over a predetermined threshold, the appliance200 can direct or distribute client requests to another server 106.

In some embodiments, the appliance 200 acts as a Domain Name Service(DNS) resolver or otherwise provides resolution of a DNS request fromclients 102. In some embodiments, the appliance intercepts a DNS requesttransmitted by the client 102. In one embodiment, the appliance 200responds to a client's DNS request with an IP address of or hosted bythe appliance 200. In this embodiment, the client 102 transmits networkcommunication for the domain name to the appliance 200. In anotherembodiment, the appliance 200 responds to a client's DNS request with anIP address of or hosted by a second appliance 200′. In some embodiments,the appliance 200 responds to a client's DNS request with an IP addressof a server 106 determined by the appliance 200.

In yet another embodiment, the appliance 200 provides applicationfirewall functionality 290 for communications between the client 102 andserver 106. In one embodiment, the policy engine 236 provides rules fordetecting and blocking illegitimate requests. In some embodiments, theapplication firewall 290 protects against denial of service (DoS)attacks. In other embodiments, the appliance inspects the content ofintercepted requests to identify and block application-based attacks. Insome embodiments, the rules/policy engine 236 comprises one or moreapplication firewall or security control policies for providingprotections against various classes and types of web or Internet basedvulnerabilities, such as one or more of the following: 1) bufferoverflow, 2) CGI-BIN parameter manipulation, 3) form/hidden fieldmanipulation, 4) forceful browsing, 5) cookie or session poisoning, 6)broken access control list (ACLs) or weak passwords, 7) cross-sitescripting (XSS), 8) command injection, 9) SQL injection, 10) errortriggering sensitive information leak, 11) insecure use of cryptography,12) server misconfiguration, 13) back doors and debug options, 14)website defacement, 15) platform or operating systems vulnerabilities,and 16) zero-day exploits. In an embodiment, the application firewall290 provides HTML form field protection in the form of inspecting oranalyzing the network communication for one or more of the following: 1)required fields are returned, 2) no added field allowed, 3) read-onlyand hidden field enforcement, 4) drop-down list and radio button fieldconformance, and 5) form-field max-length enforcement. In someembodiments, the application firewall 290 ensures cookies are notmodified. In other embodiments, the application firewall 290 protectsagainst forceful browsing by enforcing legal URLs.

In still yet other embodiments, the application firewall 290 protectsany confidential information contained in the network communication. Theapplication firewall 290 may inspect or analyze any networkcommunication in accordance with the rules or polices of the engine 236to identify any confidential information in any field of the networkpacket. In some embodiments, the application firewall 290 identifies inthe network communication one or more occurrences of a credit cardnumber, password, social security number, name, patient code, contactinformation, and age. The encoded portion of the network communicationmay comprise these occurrences or the confidential information. Based onthese occurrences, in one embodiment, the application firewall 290 maytake a policy action on the network communication, such as preventtransmission of the network communication. In another embodiment, theapplication firewall 290 may rewrite, remove or otherwise mask suchidentified occurrence or confidential information.

Still referring to FIG. 2B, the appliance 200 may include a performancemonitoring agent 197 as discussed above in conjunction with FIG. 1D. Inone embodiment, the appliance 200 receives the monitoring agent 197 fromthe monitoring service 198 or monitoring server 106 as depicted in FIG.1D. In some embodiments, the appliance 200 stores the monitoring agent197 in storage, such as disk, for delivery to any client or server incommunication with the appliance 200. For example, in one embodiment,the appliance 200 transmits the monitoring agent 197 to a client uponreceiving a request to establish a transport layer connection. In otherembodiments, the appliance 200 transmits the monitoring agent 197 uponestablishing the transport layer connection with the client 102. Inanother embodiment, the appliance 200 transmits the monitoring agent 197to the client upon intercepting or detecting a request for a web page.In yet another embodiment, the appliance 200 transmits the monitoringagent 197 to a client or a server in response to a request from themonitoring server 198. In one embodiment, the appliance 200 transmitsthe monitoring agent 197 to a second appliance 200′ or appliance 205.

In other embodiments, the appliance 200 executes the monitoring agent197. In one embodiment, the monitoring agent 197 measures and monitorsthe performance of any application, program, process, service, task orthread executing on the appliance 200. For example, the monitoring agent197 may monitor and measure performance and operation of vServers275A-275N. In another embodiment, the monitoring agent 197 measures andmonitors the performance of any transport layer connections of theappliance 200. In some embodiments, the monitoring agent 197 measuresand monitors the performance of any user sessions traversing theappliance 200. In one embodiment, the monitoring agent 197 measures andmonitors the performance of any virtual private network connectionsand/or sessions traversing the appliance 200, such an SSL VPN session.In still further embodiments, the monitoring agent 197 measures andmonitors the memory, CPU and disk usage and performance of the appliance200. In yet another embodiment, the monitoring agent 197 measures andmonitors the performance of any acceleration technique 288 performed bythe appliance 200, such as SSL offloading, connection pooling andmultiplexing, caching, and compression. In some embodiments, themonitoring agent 197 measures and monitors the performance of any loadbalancing and/or content switching 284 performed by the appliance 200.In other embodiments, the monitoring agent 197 measures and monitors theperformance of application firewall 290 protection and processingperformed by the appliance 200.

C. Client Agent

Referring now to FIG. 3, an embodiment of the client agent 120 isdepicted. The client 102 includes a client agent 120 for establishingand exchanging communications with the appliance 200 and/or server 106via a network 104. In brief overview, the client 102 operates oncomputing device 100 having an operating system with a kernel mode 302and a user mode 303, and a network stack 310 with one or more layers 310a-310 b. The client 102 may have installed and/or execute one or moreapplications. In some embodiments, one or more applications maycommunicate via the network stack 310 to a network 104. One of theapplications, such as a web browser, may also include a first program322. For example, the first program 322 may be used in some embodimentsto install and/or execute the client agent 120, or any portion thereof.The client agent 120 includes an interception mechanism, or interceptor350, for intercepting network communications from the network stack 310from the one or more applications.

The network stack 310 of the client 102 may comprise any type and formof software, or hardware, or any combinations thereof, for providingconnectivity to and communications with a network. In one embodiment,the network stack 310 comprises a software implementation for a networkprotocol suite. The network stack 310 may comprise one or more networklayers, such as any networks layers of the Open Systems Interconnection(OSI) communications model as those skilled in the art recognize andappreciate. As such, the network stack 310 may comprise any type andform of protocols for any of the following layers of the OSI model: 1)physical link layer, 2) data link layer, 3) network layer, 4) transportlayer, 5) session layer, 6) presentation layer, and 7) applicationlayer. In one embodiment, the network stack 310 may comprise a transportcontrol protocol (TCP) over the network layer protocol of the internetprotocol (IP), generally referred to as TCP/IP. In some embodiments, theTCP/IP protocol may be carried over the Ethernet protocol, which maycomprise any of the family of IEEE wide-area-network (WAN) orlocal-area-network (LAN) protocols, such as those protocols covered bythe IEEE 802.3. In some embodiments, the network stack 310 comprises anytype and form of a wireless protocol, such as IEEE 802.11 and/or mobileinternet protocol.

In view of a TCP/IP based network, any TCP/IP based protocol may beused, including Messaging Application Programming Interface (MAPI)(email), File Transfer Protocol (FTP), HyperText Transfer Protocol(HTTP), Common Internet File System (CIF S) protocol (file transfer),Independent Computing Architecture (ICA) protocol, Remote DesktopProtocol (RDP), Wireless Application Protocol (WAP), Mobile IP protocol,and Voice Over IP (VoIP) protocol. In another embodiment, the networkstack 310 comprises any type and form of transport control protocol,such as a modified transport control protocol, for example a TransactionTCP (T/TCP), TCP with selection acknowledgements (TCP-SACK), TCP withlarge windows (TCP-LW), a congestion prediction protocol such as theTCP-Vegas protocol, and a TCP spoofing protocol. In other embodiments,any type and form of user datagram protocol (UDP), such as UDP over IP,may be used by the network stack 310, such as for voice communicationsor real-time data communications.

Furthermore, the network stack 310 may include one or more networkdrivers supporting the one or more layers, such as a TCP driver or anetwork layer driver. The network drivers may be included as part of theoperating system of the computing device 100 or as part of any networkinterface cards or other network access components of the computingdevice 100. In some embodiments, any of the network drivers of thenetwork stack 310 may be customized, modified or adapted to provide acustom or modified portion of the network stack 310 in support of any ofthe techniques described herein. In other embodiments, the accelerationprogram 302 is designed and constructed to operate with or work inconjunction with the network stack 310 installed or otherwise providedby the operating system of the client 102.

The network stack 310 comprises any type and form of interfaces forreceiving, obtaining, providing or otherwise accessing any informationand data related to network communications of the client 102. In oneembodiment, an interface to the network stack 310 comprises anapplication programming interface (API). The interface may also compriseany function call, hooking or filtering mechanism, event or call backmechanism, or any type of interfacing technique. The network stack 310via the interface may receive or provide any type and form of datastructure, such as an object, related to functionality or operation ofthe network stack 310. For example, the data structure may compriseinformation and data related to a network packet or one or more networkpackets. In some embodiments, the data structure comprises a portion ofthe network packet processed at a protocol layer of the network stack310, such as a network packet of the transport layer. In someembodiments, the data structure 325 comprises a kernel-level datastructure, while in other embodiments, the data structure 325 comprisesa user-mode data structure. A kernel-level data structure may comprise adata structure obtained or related to a portion of the network stack 310operating in kernel-mode 302, or a network driver or other softwarerunning in kernel-mode 302, or any data structure obtained or receivedby a service, process, task, thread or other executable instructionsrunning or operating in kernel-mode of the operating system.

Additionally, some portions of the network stack 310 may execute oroperate in kernel-mode 302, for example, the data link or network layer,while other portions execute or operate in user-mode 303, such as anapplication layer of the network stack 310. For example, a first portion310 a of the network stack may provide user-mode access to the networkstack 310 to an application while a second portion 310 a of the networkstack 310 provides access to a network. In some embodiments, a firstportion 310 a of the network stack may comprise one or more upper layersof the network stack 310, such as any of layers 5-7. In otherembodiments, a second portion 310 b of the network stack 310 comprisesone or more lower layers, such as any of layers 1-4. Each of the firstportion 310 a and second portion 310 b of the network stack 310 maycomprise any portion of the network stack 310, at any one or morenetwork layers, in user-mode 203, kernel-mode, 202, or combinationsthereof, or at any portion of a network layer or interface point to anetwork layer or any portion of or interface point to the user-mode 203and kernel-mode 203.

The interceptor 350 may comprise software, hardware, or any combinationof software and hardware. In one embodiment, the interceptor 350intercept a network communication at any point in the network stack 310,and redirects or transmits the network communication to a destinationdesired, managed or controlled by the interceptor 350 or client agent120. For example, the interceptor 350 may intercept a networkcommunication of a network stack 310 of a first network and transmit thenetwork communication to the appliance 200 for transmission on a secondnetwork 104. In some embodiments, the interceptor 350 comprises any typeinterceptor 350 comprises a driver, such as a network driver constructedand designed to interface and work with the network stack 310. In someembodiments, the client agent 120 and/or interceptor 350 operates at oneor more layers of the network stack 310, such as at the transport layer.In one embodiment, the interceptor 350 comprises a filter driver,hooking mechanism, or any form and type of suitable network driverinterface that interfaces to the transport layer of the network stack,such as via the transport driver interface (TDI). In some embodiments,the interceptor 350 interfaces to a first protocol layer, such as thetransport layer and another protocol layer, such as any layer above thetransport protocol layer, for example, an application protocol layer. Inone embodiment, the interceptor 350 may comprise a driver complying withthe Network Driver Interface Specification (NDIS), or a NDIS driver. Inanother embodiment, the interceptor 350 may comprise a mini-filter or amini-port driver. In one embodiment, the interceptor 350, or portionthereof, operates in kernel-mode 202. In another embodiment, theinterceptor 350, or portion thereof, operates in user-mode 203. In someembodiments, a portion of the interceptor 350 operates in kernel-mode202 while another portion of the interceptor 350 operates in user-mode203. In other embodiments, the client agent 120 operates in user-mode203 but interfaces via the interceptor 350 to a kernel-mode driver,process, service, task or portion of the operating system, such as toobtain a kernel-level data structure 225. In further embodiments, theinterceptor 350 is a user-mode application or program, such asapplication.

In one embodiment, the interceptor 350 intercepts any transport layerconnection requests. In these embodiments, the interceptor 350 executetransport layer application programming interface (API) calls to set thedestination information, such as destination IP address and/or port to adesired location for the location. In this manner, the interceptor 350intercepts and redirects the transport layer connection to a IP addressand port controlled or managed by the interceptor 350 or client agent120. In one embodiment, the interceptor 350 sets the destinationinformation for the connection to a local IP address and port of theclient 102 on which the client agent 120 is listening. For example, theclient agent 120 may comprise a proxy service listening on a local IPaddress and port for redirected transport layer communications. In someembodiments, the client agent 120 then communicates the redirectedtransport layer communication to the appliance 200.

In some embodiments, the interceptor 350 intercepts a Domain NameService (DNS) request. In one embodiment, the client agent 120 and/orinterceptor 350 resolves the DNS request. In another embodiment, theinterceptor transmits the intercepted DNS request to the appliance 200for DNS resolution. In one embodiment, the appliance 200 resolves theDNS request and communicates the DNS response to the client agent 120.In some embodiments, the appliance 200 resolves the DNS request viaanother appliance 200′ or a DNS server 106.

In yet another embodiment, the client agent 120 may comprise two agents120 and 120′. In one embodiment, a first agent 120 may comprise aninterceptor 350 operating at the network layer of the network stack 310.In some embodiments, the first agent 120 intercepts network layerrequests such as Internet Control Message Protocol (ICMP) requests(e.g., ping and traceroute). In other embodiments, the second agent 120′may operate at the transport layer and intercept transport layercommunications. In some embodiments, the first agent 120 interceptscommunications at one layer of the network stack 210 and interfaces withor communicates the intercepted communication to the second agent 120′.

The client agent 120 and/or interceptor 350 may operate at or interfacewith a protocol layer in a manner transparent to any other protocollayer of the network stack 310. For example, in one embodiment, theinterceptor 350 operates or interfaces with the transport layer of thenetwork stack 310 transparently to any protocol layer below thetransport layer, such as the network layer, and any protocol layer abovethe transport layer, such as the session, presentation or applicationlayer protocols. This allows the other protocol layers of the networkstack 310 to operate as desired and without modification for using theinterceptor 350. As such, the client agent 120 and/or interceptor 350can interface with the transport layer to secure, optimize, accelerate,route or load-balance any communications provided via any protocolcarried by the transport layer, such as any application layer protocolover TCP/IP.

Furthermore, the client agent 120 and/or interceptor may operate at orinterface with the network stack 310 in a manner transparent to anyapplication, a user of the client 102, and any other computing device,such as a server, in communications with the client 102. The clientagent 120 and/or interceptor 350 may be installed and/or executed on theclient 102 in a manner without modification of an application. In someembodiments, the user of the client 102 or a computing device incommunications with the client 102 are not aware of the existence,execution or operation of the client agent 120 and/or interceptor 350.As such, in some embodiments, the client agent 120 and/or interceptor350 is installed, executed, and/or operated transparently to anapplication, user of the client 102, another computing device, such as aserver, or any of the protocol layers above and/or below the protocollayer interfaced to by the interceptor 350.

The client agent 120 includes an acceleration program 302, a streamingclient 306, a collection agent 304, and/or monitoring agent 197. In oneembodiment, the client agent 120 comprises an Independent ComputingArchitecture (ICA) client, or any portion thereof, developed by CitrixSystems, Inc. of Fort Lauderdale, Fla., and is also referred to as anICA client. In some embodiments, the client 120 comprises an applicationstreaming client 306 for streaming an application from a server 106 to aclient 102. In some embodiments, the client agent 120 comprises anacceleration program 302 for accelerating communications between client102 and server 106. In another embodiment, the client agent 120 includesa collection agent 304 for performing end-point detection/scanning andcollecting end-point information for the appliance 200 and/or server106.

In some embodiments, the acceleration program 302 comprises aclient-side acceleration program for performing one or more accelerationtechniques to accelerate, enhance or otherwise improve a client'scommunications with and/or access to a server 106, such as accessing anapplication provided by a server 106. The logic, functions, and/oroperations of the executable instructions of the acceleration program302 may perform one or more of the following acceleration techniques: 1)multi-protocol compression, 2) transport control protocol pooling, 3)transport control protocol multiplexing, 4) transport control protocolbuffering, and 5) caching via a cache manager. Additionally, theacceleration program 302 may perform encryption and/or decryption of anycommunications received and/or transmitted by the client 102. In someembodiments, the acceleration program 302 performs one or more of theacceleration techniques in an integrated manner or fashion.Additionally, the acceleration program 302 can perform compression onany of the protocols, or multiple-protocols, carried as a payload of anetwork packet of the transport layer protocol.

The streaming client 306 comprises an application, program, process,service, task or executable instructions for receiving and executing astreamed application from a server 106. A server 106 may stream one ormore application data files to the streaming client 306 for playing,executing or otherwise causing to be executed the application on theclient 102. In some embodiments, the server 106 transmits a set ofcompressed or packaged application data files to the streaming client306. In some embodiments, the plurality of application files arecompressed and stored on a file server within an archive file such as aCAB, ZIP, SIT, TAR, JAR or other archive. In one embodiment, the server106 decompresses, unpackages or unarchives the application files andtransmits the files to the client 102. In another embodiment, the client102 decompresses, unpackages or unarchives the application files. Thestreaming client 306 dynamically installs the application, or portionthereof, and executes the application. In one embodiment, the streamingclient 306 may be an executable program. In some embodiments, thestreaming client 306 may be able to launch another executable program.

The collection agent 304 comprises an application, program, process,service, task or executable instructions for identifying, obtainingand/or collecting information about the client 102. In some embodiments,the appliance 200 transmits the collection agent 304 to the client 102or client agent 120. The collection agent 304 may be configuredaccording to one or more policies of the policy engine 236 of theappliance. In other embodiments, the collection agent 304 transmitscollected information on the client 102 to the appliance 200. In oneembodiment, the policy engine 236 of the appliance 200 uses thecollected information to determine and provide access, authenticationand authorization control of the client's connection to a network 104.

In one embodiment, the collection agent 304 comprises an end-pointdetection and scanning mechanism, which identifies and determines one ormore attributes or characteristics of the client. For example, thecollection agent 304 may identify and determine any one or more of thefollowing client-side attributes: 1) the operating system and/or aversion of an operating system, 2) a service pack of the operatingsystem, 3) a running service, 4) a running process, and 5) a file. Thecollection agent 304 may also identify and determine the presence orversions of any one or more of the following on the client: 1) antivirussoftware, 2) personal firewall software, 3) anti-spam software, and 4)internet security software. The policy engine 236 may have one or morepolicies based on any one or more of the attributes or characteristicsof the client or client-side attributes.

In some embodiments, the client agent 120 includes a monitoring agent197 as discussed in conjunction with FIGS. 1D and 2B. The monitoringagent 197 may be any type and form of script, such as Visual Basic orJava script. In one embodiment, the monitoring agent 197 monitors andmeasures performance of any portion of the client agent 120. Forexample, in some embodiments, the monitoring agent 197 monitors andmeasures performance of the acceleration program 302. In anotherembodiment, the monitoring agent 197 monitors and measures performanceof the streaming client 306. In other embodiments, the monitoring agent197 monitors and measures performance of the collection agent 304. Instill another embodiment, the monitoring agent 197 monitors and measuresperformance of the interceptor 350. In some embodiments, the monitoringagent 197 monitors and measures any resource of the client 102, such asmemory, CPU and disk.

The monitoring agent 197 may monitor and measure performance of anyapplication of the client. In one embodiment, the monitoring agent 197monitors and measures performance of a browser on the client 102. Insome embodiments, the monitoring agent 197 monitors and measuresperformance of any application delivered via the client agent 120. Inother embodiments, the monitoring agent 197 measures and monitors enduser response times for an application, such as web-based or HTTPresponse times. The monitoring agent 197 may monitor and measureperformance of an ICA or RDP client. In another embodiment, themonitoring agent 197 measures and monitors metrics for a user session orapplication session. In some embodiments, monitoring agent 197 measuresand monitors an ICA or RDP session. In one embodiment, the monitoringagent 197 measures and monitors the performance of the appliance 200 inaccelerating delivery of an application and/or data to the client 102.

In some embodiments and still referring to FIG. 3, a first program 322may be used to install and/or execute the client agent 120, or portionthereof, such as the interceptor 350, automatically, silently,transparently, or otherwise. In one embodiment, the first program 322comprises a plugin component, such an ActiveX control or Java control orscript that is loaded into and executed by an application. For example,the first program comprises an ActiveX control loaded and run by a webbrowser application, such as in the memory space or context of theapplication. In another embodiment, the first program 322 comprises aset of executable instructions loaded into and run by the application,such as a browser. In one embodiment, the first program 322 comprises adesigned and constructed program to install the client agent 120. Insome embodiments, the first program 322 obtains, downloads, or receivesthe client agent 120 via the network from another computing device. Inanother embodiment, the first program 322 is an installer program or aplug and play manager for installing programs, such as network drivers,on the operating system of the client 102.

D. Systems and Methods for Providing Virtualized Application DeliveryController

Referring now to FIG. 4A, a block diagram depicts one embodiment of avirtualization environment 400. In brief overview, a computing device100 includes a hypervisor layer, a virtualization layer, and a hardwarelayer. The hypervisor layer includes a hypervisor 401 (also referred toas a virtualization manager) that allocates and manages access to anumber of physical resources in the hardware layer (e.g., theprocessor(s) 421, and disk(s) 428) by at least one virtual machineexecuting in the virtualization layer. The virtualization layer includesat least one operating system 410 and a plurality of virtual resourcesallocated to the at least one operating system 410. Virtual resourcesmay include, without limitation, a plurality of virtual processors 432a, 432 b, 432 c (generally 432), and virtual disks 442 a, 442 b, 442 c(generally 442), as well as virtual resources such as virtual memory andvirtual network interfaces. The plurality of virtual resources and theoperating system 410 may be referred to as a virtual machine 406. Avirtual machine 406 may include a control operating system 405 incommunication with the hypervisor 401 and used to execute applicationsfor managing and configuring other virtual machines on the computingdevice 100.

In greater detail, a hypervisor 401 may provide virtual resources to anoperating system in any manner which simulates the operating systemhaving access to a physical device. A hypervisor 401 may provide virtualresources to any number of guest operating systems 410 a, 410 b(generally 410). In some embodiments, a computing device 100 executesone or more types of hypervisors. In these embodiments, hypervisors maybe used to emulate virtual hardware, partition physical hardware,virtualize physical hardware, and execute virtual machines that provideaccess to computing environments. Hypervisors may include thosemanufactured by VMWare, Inc., of Palo Alto, Calif.; the XEN hypervisor,an open source product whose development is overseen by the open sourceXen.org community; HyperV, VirtualServer or virtual PC hypervisorsprovided by Microsoft, or others. In some embodiments, a computingdevice 100 executing a hypervisor that creates a virtual machineplatform on which guest operating systems may execute is referred to asa host server. In one of these embodiments, for example, the computingdevice 100 is a XEN SERVER provided by Citrix Systems, Inc., of FortLauderdale, Fla.

In some embodiments, a hypervisor 401 executes within an operatingsystem executing on a computing device. In one of these embodiments, acomputing device executing an operating system and a hypervisor 401 maybe said to have a host operating system (the operating system executingon the computing device), and a guest operating system (an operatingsystem executing within a computing resource partition provided by thehypervisor 401). In other embodiments, a hypervisor 401 interactsdirectly with hardware on a computing device, instead of executing on ahost operating system. In one of these embodiments, the hypervisor 401may be said to be executing on “bare metal,” referring to the hardwarecomprising the computing device.

In some embodiments, a hypervisor 401 may create a virtual machine 406a-c (generally 406) in which an operating system 410 executes. In one ofthese embodiments, for example, the hypervisor 401 loads a virtualmachine image to create a virtual machine 406. In another of theseembodiments, the hypervisor 401 executes an operating system 410 withinthe virtual machine 406. In still another of these embodiments, thevirtual machine 406 executes an operating system 410.

In some embodiments, the hypervisor 401 controls processor schedulingand memory partitioning for a virtual machine 406 executing on thecomputing device 100. In one of these embodiments, the hypervisor 401controls the execution of at least one virtual machine 406. In anotherof these embodiments, the hypervisor 401 presents at least one virtualmachine 406 with an abstraction of at least one hardware resourceprovided by the computing device 100. In other embodiments, thehypervisor 401 controls whether and how physical processor capabilitiesare presented to the virtual machine 406.

A control operating system 405 may execute at least one application formanaging and configuring the guest operating systems. In one embodiment,the control operating system 405 may execute an administrativeapplication, such as an application including a user interface providingadministrators with access to functionality for managing the executionof a virtual machine, including functionality for executing a virtualmachine, terminating an execution of a virtual machine, or identifying atype of physical resource for allocation to the virtual machine. Inanother embodiment, the hypervisor 401 executes the control operatingsystem 405 within a virtual machine 406 created by the hypervisor 401.In still another embodiment, the control operating system 405 executesin a virtual machine 406 that is authorized to directly access physicalresources on the computing device 100. In some embodiments, a controloperating system 405 a on a computing device 100 a may exchange datawith a control operating system 405 b on a computing device 100 b, viacommunications between a hypervisor 401 a and a hypervisor 401 b. Inthis way, one or more computing devices 100 may exchange data with oneor more of the other computing devices 100 regarding processors andother physical resources available in a pool of resources. In one ofthese embodiments, this functionality allows a hypervisor to manage apool of resources distributed across a plurality of physical computingdevices. In another of these embodiments, multiple hypervisors manageone or more of the guest operating systems executed on one of thecomputing devices 100.

In one embodiment, the control operating system 405 executes in avirtual machine 406 that is authorized to interact with at least oneguest operating system 410. In another embodiment, a guest operatingsystem 410 communicates with the control operating system 405 via thehypervisor 401 in order to request access to a disk or a network. Instill another embodiment, the guest operating system 410 and the controloperating system 405 may communicate via a communication channelestablished by the hypervisor 401, such as, for example, via a pluralityof shared memory pages made available by the hypervisor 401.

In some embodiments, the control operating system 405 includes a networkback-end driver for communicating directly with networking hardwareprovided by the computing device 100. In one of these embodiments, thenetwork back-end driver processes at least one virtual machine requestfrom at least one guest operating system 110. In other embodiments, thecontrol operating system 405 includes a block back-end driver forcommunicating with a storage element on the computing device 100. In oneof these embodiments, the block back-end driver reads and writes datafrom the storage element based upon at least one request received from aguest operating system 410.

In one embodiment, the control operating system 405 includes a toolsstack 404. In another embodiment, a tools stack 404 providesfunctionality for interacting with the hypervisor 401, communicatingwith other control operating systems 405 (for example, on a secondcomputing device 100 b), or managing virtual machines 406 b, 406 c onthe computing device 100. In another embodiment, the tools stack 404includes customized applications for providing improved managementfunctionality to an administrator of a virtual machine farm. In someembodiments, at least one of the tools stack 404 and the controloperating system 405 include a management API that provides an interfacefor remotely configuring and controlling virtual machines 406 running ona computing device 100. In other embodiments, the control operatingsystem 405 communicates with the hypervisor 401 through the tools stack404.

In one embodiment, the hypervisor 401 executes a guest operating system410 within a virtual machine 406 created by the hypervisor 401. Inanother embodiment, the guest operating system 410 provides a user ofthe computing device 100 with access to resources within a computingenvironment. In still another embodiment, a resource includes a program,an application, a document, a file, a plurality of applications, aplurality of files, an executable program file, a desktop environment, acomputing environment, or other resource made available to a user of thecomputing device 100. In yet another embodiment, the resource may bedelivered to the computing device 100 via a plurality of access methodsincluding, but not limited to, conventional installation directly on thecomputing device 100, delivery to the computing device 100 via a methodfor application streaming, delivery to the computing device 100 ofoutput data generated by an execution of the resource on a secondcomputing device 100′ and communicated to the computing device 100 via apresentation layer protocol, delivery to the computing device 100 ofoutput data generated by an execution of the resource via a virtualmachine executing on a second computing device 100′, or execution from aremovable storage device connected to the computing device 100, such asa USB device, or via a virtual machine executing on the computing device100 and generating output data. In some embodiments, the computingdevice 100 transmits output data generated by the execution of theresource to another computing device 100′.

In one embodiment, the guest operating system 410, in conjunction withthe virtual machine on which it executes, forms a fully-virtualizedvirtual machine which is not aware that it is a virtual machine; such amachine may be referred to as a “Domain U HVM (Hardware Virtual Machine)virtual machine”. In another embodiment, a fully-virtualized machineincludes software emulating a Basic Input/Output System (BIOS) in orderto execute an operating system within the fully-virtualized machine. Instill another embodiment, a fully-virtualized machine may include adriver that provides functionality by communicating with the hypervisor401. In such an embodiment, the driver may be aware that it executeswithin a virtualized environment. In another embodiment, the guestoperating system 410, in conjunction with the virtual machine on whichit executes, forms a paravirtualized virtual machine, which is awarethat it is a virtual machine; such a machine may be referred to as a“Domain U PV virtual machine”. In another embodiment, a paravirtualizedmachine includes additional drivers that a fully-virtualized machinedoes not include. In still another embodiment, the paravirtualizedmachine includes the network back-end driver and the block back-enddriver included in a control operating system 405, as described above.

Referring now to FIG. 4B, a block diagram depicts one embodiment of aplurality of networked computing devices in a system in which at leastone physical host executes a virtual machine. In brief overview, thesystem includes a management component 404 and a hypervisor 401. Thesystem includes a plurality of computing devices 100, a plurality ofvirtual machines 406, a plurality of hypervisors 401, a plurality ofmanagement components referred to variously as tools stacks 404 ormanagement components 404, and a physical resource 421, 428. Theplurality of physical machines 100 may each be provided as computingdevices 100, described above in connection with FIGS. 1E-1H and 4A.

In greater detail, a physical disk 428 is provided by a computing device100 and stores at least a portion of a virtual disk 442. In someembodiments, a virtual disk 442 is associated with a plurality ofphysical disks 428. In one of these embodiments, one or more computingdevices 100 may exchange data with one or more of the other computingdevices 100 regarding processors and other physical resources availablein a pool of resources, allowing a hypervisor to manage a pool ofresources distributed across a plurality of physical computing devices.In some embodiments, a computing device 100 on which a virtual machine406 executes is referred to as a physical host 100 or as a host machine100.

The hypervisor executes on a processor on the computing device 100. Thehypervisor allocates, to a virtual disk, an amount of access to thephysical disk. In one embodiment, the hypervisor 401 allocates an amountof space on the physical disk. In another embodiment, the hypervisor 401allocates a plurality of pages on the physical disk. In someembodiments, the hypervisor provisions the virtual disk 442 as part of aprocess of initializing and executing a virtual machine 450.

In one embodiment, the management component 404 a is referred to as apool management component 404 a. In another embodiment, a managementoperating system 405 a, which may be referred to as a control operatingsystem 405 a, includes the management component. In some embodiments,the management component is referred to as a tools stack. In one ofthese embodiments, the management component is the tools stack 404described above in connection with FIG. 4A. In other embodiments, themanagement component 404 provides a user interface for receiving, from auser such as an administrator, an identification of a virtual machine406 to provision and/or execute. In still other embodiments, themanagement component 404 provides a user interface for receiving, from auser such as an administrator, the request for migration of a virtualmachine 406 b from one physical machine 100 to another. In furtherembodiments, the management component 404 a identifies a computingdevice 100 b on which to execute a requested virtual machine 406 d andinstructs the hypervisor 401 b on the identified computing device 100 bto execute the identified virtual machine; such a management componentmay be referred to as a pool management component.

Referring now to FIG. 4C, embodiments of a virtual application deliverycontroller or virtual appliance 450 are depicted. In brief overview, anyof the functionality and/or embodiments of the appliance 200 (e.g., anapplication delivery controller) described above in connection withFIGS. 2A and 2B may be deployed in any embodiment of the virtualizedenvironment described above in connection with FIGS. 4A and 4B. Insteadof the functionality of the application delivery controller beingdeployed in the form of an appliance 200, such functionality may bedeployed in a virtualized environment 400 on any computing device 100,such as a client 102, server 106 or appliance 200.

Referring now to FIG. 4C, a diagram of an embodiment of a virtualappliance 450 operating on a hypervisor 401 of a server 106 is depicted.As with the appliance 200 of FIGS. 2A and 2B, the virtual appliance 450may provide functionality for availability, performance, offload andsecurity. For availability, the virtual appliance may perform loadbalancing between layers 4 and 7 of the network and may also performintelligent service health monitoring. For performance increases vianetwork traffic acceleration, the virtual appliance may perform cachingand compression. To offload processing of any servers, the virtualappliance may perform connection multiplexing and pooling and/or SSLprocessing. For security, the virtual appliance may perform any of theapplication firewall functionality and SSL VPN function of appliance200.

Any of the modules of the appliance 200 as described in connection withFIG. 2A may be packaged, combined, designed or constructed in a form ofthe virtualized appliance delivery controller 450 deployable as one ormore software modules or components executable in a virtualizedenvironment 300 or non-virtualized environment on any server, such as anoff the shelf server. For example, the virtual appliance may be providedin the form of an installation package to install on a computing device.With reference to FIG. 2A, any of the cache manager 232, policy engine236, compression 238, encryption engine 234, packet engine 240, GUI 210,CLI 212, shell services 214 and health monitoring programs 216 may bedesigned and constructed as a software component or module to run on anyoperating system of a computing device and/or of a virtualizedenvironment 300. Instead of using the encryption processor 260,processor 262, memory 264 and network stack 267 of the appliance 200,the virtualized appliance 400 may use any of these resources as providedby the virtualized environment 400 or as otherwise available on theserver 106.

Still referring to FIG. 4C, and in brief overview, any one or morevServers 275A-275N may be in operation or executed in a virtualizedenvironment 400 of any type of computing device 100, such as any server106. Any of the modules or functionality of the appliance 200 describedin connection with FIG. 2B may be designed and constructed to operate ineither a virtualized or non-virtualized environment of a server. Any ofthe vServer 275, SSL VPN 280, Intranet UP 282, Switching 284, DNS 286,acceleration 288, App FW 290 and monitoring agent may be packaged,combined, designed or constructed in a form of application deliverycontroller 450 deployable as one or more software modules or componentsexecutable on a device and/or virtualized environment 400.

In some embodiments, a server may execute multiple virtual machines 406a-406 n in the virtualization environment with each virtual machinerunning the same or different embodiments of the virtual applicationdelivery controller 450. In some embodiments, the server may execute oneor more virtual appliances 450 on one or more virtual machines on a coreof a multi-core processing system. In some embodiments, the server mayexecute one or more virtual appliances 450 on one or more virtualmachines on each processor of a multiple processor device.

E. Systems and Methods for Providing a Multi-Core Architecture

In accordance with Moore's Law, the number of transistors that may beplaced on an integrated circuit may double approximately every twoyears. However, CPU speed increases may reach plateaus, for example CPUspeed has been around 3.5-4 GHz range since 2005. In some cases, CPUmanufacturers may not rely on CPU speed increases to gain additionalperformance. Some CPU manufacturers may add additional cores to theirprocessors to provide additional performance. Products, such as those ofsoftware and networking vendors, that rely on CPUs for performance gainsmay improve their performance by leveraging these multi-core CPUs. Thesoftware designed and constructed for a single CPU may be redesignedand/or rewritten to take advantage of a multi-threaded, parallelarchitecture or otherwise a multi-core architecture.

A multi-core architecture of the appliance 200, referred to as nCore ormulti-core technology, allows the appliance in some embodiments to breakthe single core performance barrier and to leverage the power ofmulti-core CPUs. In the previous architecture described in connectionwith FIG. 2A, a single network or packet engine is run. The multiplecores of the nCore technology and architecture allow multiple packetengines to run concurrently and/or in parallel. With a packet enginerunning on each core, the appliance architecture leverages theprocessing capacity of additional cores. In some embodiments, thisprovides up to a 7× increase in performance and scalability.

Illustrated in FIG. 5A are some embodiments of work, task, load ornetwork traffic distribution across one or more processor coresaccording to a type of parallelism or parallel computing scheme, such asfunctional parallelism, data parallelism or flow-based data parallelism.In brief overview, FIG. 5A illustrates embodiments of a multi-coresystem such as an appliance 200′ with n-cores, a total of cores numbers1 through N. In one embodiment, work, load or network traffic can bedistributed among a first core 505A, a second core 505B, a third core505C, a fourth core 505D, a fifth core 505E, a sixth core 505F, aseventh core 505G, and so on such that distribution is across all or twoor more of the n cores 505N (hereinafter referred to collectively ascores 505.) There may be multiple VIPs 275 each running on a respectivecore of the plurality of cores. There may be multiple packet engines 240each running on a respective core of the plurality of cores. Any of theapproaches used may lead to different, varying or similar work load orperformance level 515 across any of the cores. For a functionalparallelism approach, each core may run a different function of thefunctionalities provided by the packet engine, a VIP 275 or appliance200. In a data parallelism approach, data may be paralleled ordistributed across the cores based on the Network Interface Card (NIC)or VIP 275 receiving the data. In another data parallelism approach,processing may be distributed across the cores by distributing dataflows to each core.

In further detail to FIG. 5A, in some embodiments, load, work or networktraffic can be distributed among cores 505 according to functionalparallelism 500. Functional parallelism may be based on each coreperforming one or more respective functions. In some embodiments, afirst core may perform a first function while a second core performs asecond function. In functional parallelism approach, the functions to beperformed by the multi-core system are divided and distributed to eachcore according to functionality. In some embodiments, functionalparallelism may be referred to as task parallelism and may be achievedwhen each processor or core executes a different process or function onthe same or different data. The core or processor may execute the sameor different code. In some cases, different execution threads or codemay communicate with one another as they work. Communication may takeplace to pass data from one thread to the next as part of a workflow.

In some embodiments, distributing work across the cores 505 according tofunctional parallelism 500, can comprise distributing network trafficaccording to a particular function such as network input/outputmanagement (NW I/O) 510A, secure sockets layer (SSL) encryption anddecryption 510B and transmission control protocol (TCP) functions 510C.This may lead to a work, performance or computing load 515 based on avolume or level of functionality being used. In some embodiments,distributing work across the cores 505 according to data parallelism540, can comprise distributing an amount of work 515 based ondistributing data associated with a particular hardware or softwarecomponent. In some embodiments, distributing work across the cores 505according to flow-based data parallelism 520, can comprise distributingdata based on a context or flow such that the amount of work 515A-N oneach core may be similar, substantially equal or relatively evenlydistributed.

In the case of the functional parallelism approach, each core may beconfigured to run one or more functionalities of the plurality offunctionalities provided by the packet engine or VIP of the appliance.For example, core 1 may perform network I/O processing for the appliance200′ while core 2 performs TCP connection management for the appliance.Likewise, core 3 may perform SSL offloading while core 4 may performlayer 7 or application layer processing and traffic management. Each ofthe cores may perform the same function or different functions. Each ofthe cores may perform more than one function. Any of the cores may runany of the functionality or portions thereof identified and/or describedin conjunction with FIGS. 2A and 2B. In this the approach, the workacross the cores may be divided by function in either a coarse-grainedor fine-grained manner. In some cases, as illustrated in FIG. 5A,division by function may lead to different cores running at differentlevels of performance or load 515.

In the case of the functional parallelism approach, each core may beconfigured to run one or more functionalities of the plurality offunctionalities provided by the packet engine of the appliance. Forexample, core 1 may perform network I/O processing for the appliance200′ while core 2 performs TCP connection management for the appliance.Likewise, core 3 may perform SSL offloading while core 4 may performlayer 7 or application layer processing and traffic management. Each ofthe cores may perform the same function or different functions. Each ofthe cores may perform more than one function. Any of the cores may runany of the functionality or portions thereof identified and/or describedin conjunction with FIGS. 2A and 2B. In this the approach, the workacross the cores may be divided by function in either a coarse-grainedor fine-grained manner. In some cases, as illustrated in FIG. 5Adivision by function may lead to different cores running at differentlevels of load or performance.

The functionality or tasks may be distributed in any arrangement andscheme. For example, FIG. 5B illustrates a first core, Core 1 505A,processing applications and processes associated with network I/Ofunctionality 510A. Network traffic associated with network I/O, in someembodiments, can be associated with a particular port number. Thus,outgoing and incoming packets having a port destination associated withNW I/O 510A will be directed towards Core 1 505A which is dedicated tohandling all network traffic associated with the NW I/O port. Similarly,Core 2 505B is dedicated to handling functionality associated with SSLprocessing and Core 4 505D may be dedicated handling all TCP levelprocessing and functionality.

While FIG. 5A illustrates functions such as network I/O, SSL and TCP,other functions can be assigned to cores. These other functions caninclude any one or more of the functions or operations described herein.For example, any of the functions described in conjunction with FIGS. 2Aand 2B may be distributed across the cores on a functionality basis. Insome cases, a first VIP 275A may run on a first core while a second VIP275B with a different configuration may run on a second core. In someembodiments, each core 505 can handle a particular functionality suchthat each core 505 can handle the processing associated with thatparticular function. For example, Core 2 505B may handle SSL offloadingwhile Core 4 505D may handle application layer processing and trafficmanagement.

In other embodiments, work, load or network traffic may be distributedamong cores 505 according to any type and form of data parallelism 540.In some embodiments, data parallelism may be achieved in a multi-coresystem by each core performing the same task or functionally ondifferent pieces of distributed data. In some embodiments, a singleexecution thread or code controls operations on all pieces of data. Inother embodiments, different threads or instructions control theoperation, but may execute the same code. In some embodiments, dataparallelism is achieved from the perspective of a packet engine,vServers (VIPs) 275A-C, network interface cards (NIC) 542D-E and/or anyother networking hardware or software included on or associated with anappliance 200. For example, each core may run the same packet engine orVIP code or configuration but operate on different sets of distributeddata. Each networking hardware or software construct can receivedifferent, varying or substantially the same amount of data, and as aresult may have varying, different or relatively the same amount of load515.

In the case of a data parallelism approach, the work may be divided upand distributed based on VIPs, NICs and/or data flows of the VIPs orNICs. In one of these approaches, the work of the multi-core system maybe divided or distributed among the VIPs by having each VIP work on adistributed set of data. For example, each core may be configured to runone or more VIPs. Network traffic may be distributed to the core foreach VIP handling that traffic. In another of these approaches, the workof the appliance may be divided or distributed among the cores based onwhich NIC receives the network traffic. For example, network traffic ofa first NIC may be distributed to a first core while network traffic ofa second NIC may be distributed to a second core. In some cases, a coremay process data from multiple NICs.

While FIG. 5A illustrates a single vServer associated with a single core505, as is the case for VIP1 275A, VIP2 275B and VIP3 275C. In someembodiments, a single vServer can be associated with one or more cores505. In contrast, one or more vServers can be associated with a singlecore 505. Associating a vServer with a core 505 may include that core505 to process all functions associated with that particular vServer. Insome embodiments, each core executes a VIP having the same code andconfiguration. In other embodiments, each core executes a VIP having thesame code but different configuration. In some embodiments, each coreexecutes a VIP having different code and the same or differentconfiguration.

Like vServers, NICs can also be associated with particular cores 505. Inmany embodiments, NICs can be connected to one or more cores 505 suchthat when a NIC receives or transmits data packets, a particular core505 handles the processing involved with receiving and transmitting thedata packets. In one embodiment, a single NIC can be associated with asingle core 505, as is the case with NIC1 542D and NIC2 542E. In otherembodiments, one or more NICs can be associated with a single core 505.In other embodiments, a single NIC can be associated with one or morecores 505. In these embodiments, load could be distributed amongst theone or more cores 505 such that each core 505 processes a substantiallysimilar amount of load. A core 505 associated with a NIC may process allfunctions and/or data associated with that particular NIC.

While distributing work across cores based on data of VIPs or NICs mayhave a level of independency, in some embodiments, this may lead tounbalanced use of cores as illustrated by the varying loads 515 of FIG.5A.

In some embodiments, load, work or network traffic can be distributedamong cores 505 based on any type and form of data flow. In another ofthese approaches, the work may be divided or distributed among coresbased on data flows. For example, network traffic between a client and aserver traversing the appliance may be distributed to and processed byone core of the plurality of cores. In some cases, the core initiallyestablishing the session or connection may be the core for which networktraffic for that session or connection is distributed. In someembodiments, the data flow is based on any unit or portion of networktraffic, such as a transaction, a request/response communication ortraffic originating from an application on a client. In this manner andin some embodiments, data flows between clients and servers traversingthe appliance 200′ may be distributed in a more balanced manner than theother approaches.

In flow-based data parallelism 520, distribution of data is related toany type of flow of data, such as request/response pairings,transactions, sessions, connections or application communications. Forexample, network traffic between a client and a server traversing theappliance may be distributed to and processed by one core of theplurality of cores. In some cases, the core initially establishing thesession or connection may be the core for which network traffic for thatsession or connection is distributed. The distribution of data flow maybe such that each core 505 carries a substantially equal or relativelyevenly distributed amount of load, data or network traffic.

In some embodiments, the data flow is based on any unit or portion ofnetwork traffic, such as a transaction, a request/response communicationor traffic originating from an application on a client. In this mannerand in some embodiments, data flows between clients and serverstraversing the appliance 200′ may be distributed in a more balancedmanner than the other approached. In one embodiment, data flow can bedistributed based on a transaction or a series of transactions. Thistransaction, in some embodiments, can be between a client and a serverand can be characterized by an IP address or other packet identifier.For example, Core 1 505A can be dedicated to transactions between aparticular client and a particular server, therefore the load 515A onCore 1 505A may be comprised of the network traffic associated with thetransactions between the particular client and server. Allocating thenetwork traffic to Core 1 505A can be accomplished by routing all datapackets originating from either the particular client or server to Core1 505A.

While work or load can be distributed to the cores based in part ontransactions, in other embodiments load or work can be allocated on aper packet basis. In these embodiments, the appliance 200 can interceptdata packets and allocate them to a core 505 having the least amount ofload. For example, the appliance 200 could allocate a first incomingdata packet to Core 1 505A because the load 515A on Core 1 is less thanthe load 515B-N on the rest of the cores 505B-N. Once the first datapacket is allocated to Core 1 505A, the amount of load 515A on Core 1505A is increased proportional to the amount of processing resourcesneeded to process the first data packet. When the appliance 200intercepts a second data packet, the appliance 200 will allocate theload to Core 4 505D because Core 4 505D has the second least amount ofload. Allocating data packets to the core with the least amount of loadcan, in some embodiments, ensure that the load 515A-N distributed toeach core 505 remains substantially equal.

In other embodiments, load can be allocated on a per unit basis where asection of network traffic is allocated to a particular core 505. Theabove-mentioned example illustrates load balancing on a per/packetbasis. In other embodiments, load can be allocated based on a number ofpackets such that every 10, 100 or 1000 packets are allocated to thecore 505 having the least amount of load. The number of packetsallocated to a core 505 can be a number determined by an application,user or administrator and can be any number greater than zero. In stillother embodiments, load can be allocated based on a time metric suchthat packets are distributed to a particular core 505 for apredetermined amount of time. In these embodiments, packets can bedistributed to a particular core 505 for five milliseconds or for anyperiod of time determined by a user, program, system, administrator orotherwise. After the predetermined time period elapses, data packets aretransmitted to a different core 505 for the predetermined period oftime.

Flow-based data parallelism methods for distributing work, load ornetwork traffic among the one or more cores 505 can comprise anycombination of the above-mentioned embodiments. These methods can becarried out by any part of the appliance 200, by an application or setof executable instructions executing on one of the cores 505, such asthe packet engine, or by any application, program or agent executing ona computing device in communication with the appliance 200.

The functional and data parallelism computing schemes illustrated inFIG. 5A can be combined in any manner to generate a hybrid parallelismor distributed processing scheme that encompasses function parallelism500, data parallelism 540, flow-based data parallelism 520 or anyportions thereof. In some cases, the multi-core system may use any typeand form of load balancing schemes to distribute load among the one ormore cores 505. The load balancing scheme may be used in any combinationwith any of the functional and data parallelism schemes or combinationsthereof.

Illustrated in FIG. 5B is an embodiment of a multi-core system 545,which may be any type and form of one or more systems, appliances,devices or components. This system 545, in some embodiments, can beincluded within an appliance 200 having one or more processing cores505A-N. The system 545 can further include one or more packet engines(PE) or packet processing engines (PPE) 548A-N communicating with amemory bus 556. The memory bus may be used to communicate with the oneor more processing cores 505A-N. Also included within the system 545 canbe one or more network interface cards (NIC) 552 and a flow distributor550 which can further communicate with the one or more processing cores505A-N. The flow distributor 550 can comprise a Receive Side Scaler(RSS) or Receive Side Scaling (RSS) module 560.

Further referring to FIG. 5B, and in more detail, in one embodiment thepacket engine(s) 548A-N can comprise any portion of the appliance 200described herein, such as any portion of the appliance described inFIGS. 2A and 2B. The packet engine(s) 548A-N can, in some embodiments,comprise any of the following elements: the packet engine 240, a networkstack 267; a cache manager 232; a policy engine 236; a compressionengine 238; an encryption engine 234; a GUI 210; a CLI 212; shellservices 214; monitoring programs 216; and any other software orhardware element able to receive data packets from one of either thememory bus 556 or the one of more cores 505A-N. In some embodiments, thepacket engine(s) 548A-N can comprise one or more vServers 275A-N, or anyportion thereof. In other embodiments, the packet engine(s) 548A-N canprovide any combination of the following functionalities: SSL VPN 280;Intranet UP 282; switching 284; DNS 286; packet acceleration 288; App FW290; monitoring such as the monitoring provided by a monitoring agent197; functionalities associated with functioning as a TCP stack; loadbalancing; SSL offloading and processing; content switching; policyevaluation; caching; compression; encoding; decompression; decoding;application firewall functionalities; XML, processing and acceleration;and SSL VPN connectivity.

The packet engine(s) 548A-N can, in some embodiments, be associated witha particular server, user, client or network. When a packet engine 548becomes associated with a particular entity, that packet engine 548 canprocess data packets associated with that entity. For example, should apacket engine 548 be associated with a first user, that packet engine548 will process and operate on packets generated by the first user, orpackets having a destination address associated with the first user.Similarly, the packet engine 548 may choose not to be associated with aparticular entity such that the packet engine 548 can process andotherwise operate on any data packets not generated by that entity ordestined for that entity.

In some instances, the packet engine(s) 548A-N can be configured tocarry out the any of the functional and/or data parallelism schemesillustrated in FIG. 5A. In these instances, the packet engine(s) 548A-Ncan distribute functions or data among the processing cores 505A-N sothat the distribution is according to the parallelism or distributionscheme. In some embodiments, a single packet engine(s) 548A-N carriesout a load balancing scheme, while in other embodiments one or morepacket engine(s) 548A-N carry out a load balancing scheme. Each core505A-N, in one embodiment, can be associated with a particular packetengine 548 such that load balancing can be carried out by the packetengine. Load balancing may in this embodiment, require that each packetengine 548A-N associated with a core 505 communicate with the otherpacket engines associated with cores so that the packet engines 548A-Ncan collectively determine where to distribute load. One embodiment ofthis process can include an arbiter that receives votes from each packetengine for load. The arbiter can distribute load to each packet engine548A-N based in part on the age of the engine's vote and in some cases apriority value associated with the current amount of load on an engine'sassociated core 505.

Any of the packet engines running on the cores may run in user mode,kernel or any combination thereof. In some embodiments, the packetengine operates as an application or program running is user orapplication space. In these embodiments, the packet engine may use anytype and form of interface to access any functionality provided by thekernel. In some embodiments, the packet engine operates in kernel modeor as part of the kernel. In some embodiments, a first portion of thepacket engine operates in user mode while a second portion of the packetengine operates in kernel mode. In some embodiments, a first packetengine on a first core executes in kernel mode while a second packetengine on a second core executes in user mode. In some embodiments, thepacket engine or any portions thereof operates on or in conjunction withthe NIC or any drivers thereof.

In some embodiments the memory bus 556 can be any type and form ofmemory or computer bus. While a single memory bus 556 is depicted inFIG. 5B, the system 545 can comprise any number of memory buses 556. Inone embodiment, each packet engine 548 can be associated with one ormore individual memory buses 556.

The NIC 552 can in some embodiments be any of the network interfacecards or mechanisms described herein. The NIC 552 can have any number ofports. The NIC can be designed and constructed to connect to any typeand form of network 104. While a single NIC 552 is illustrated, thesystem 545 can comprise any number of NICs 552. In some embodiments,each core 505A-N can be associated with one or more single NICs 552.Thus, each core 505 can be associated with a single NIC 552 dedicated toa particular core 505.

The cores 505A-N can comprise any of the processors described herein.Further, the cores 505A-N can be configured according to any of the core505 configurations described herein. Still further, the cores 505A-N canhave any of the core 505 functionalities described herein. While FIG. 5Billustrates seven cores 505A-G, any number of cores 505 can be includedwithin the system 545. In particular, the system 545 can comprise “N”cores, where “N” is a whole number greater than zero.

A core may have or use memory that is allocated or assigned for use tothat core. The memory may be considered private or local memory of thatcore and only accessible by that core. A core may have or use memorythat is shared or assigned to multiple cores. The memory may beconsidered public or shared memory that is accessible by more than onecore. A core may use any combination of private and public memory. Withseparate address spaces for each core, some level of coordination iseliminated from the case of using the same address space. With aseparate address space, a core can perform work on information and datain the core's own address space without worrying about conflicts withother cores. Each packet engine may have a separate memory pool for TCPand/or SSL connections.

Further referring to FIG. 5B, any of the functionality and/orembodiments of the cores 505 described above in connection with FIG. 5Acan be deployed in any embodiment of the virtualized environmentdescribed above in connection with FIGS. 4A and 4B. Instead of thefunctionality of the cores 505 being deployed in the form of a physicalprocessor 505, such functionality may be deployed in a virtualizedenvironment 400 on any computing device 100, such as a client 102,server 106 or appliance 200. In other embodiments, instead of thefunctionality of the cores 505 being deployed in the form of anappliance or a single device, the functionality may be deployed acrossmultiple devices in any arrangement. For example, one device maycomprise two or more cores and another device may comprise two or morecores. For example, a multi-core system may include a cluster ofcomputing devices, a server farm or network of computing devices. Insome embodiments, instead of the functionality of the cores 505 beingdeployed in the form of cores, the functionality may be deployed on aplurality of processors, such as a plurality of single core processors.

In one embodiment, the cores 505 may be any type and form of processor.In some embodiments, a core can function substantially similar to anyprocessor or central processing unit described herein. In someembodiments, the cores 505 may comprise any portion of any processordescribed herein. While FIG. 5A illustrates seven cores, there can existany “N” number of cores within an appliance 200, where “N” is any wholenumber greater than one. In some embodiments, the cores 505 can beinstalled within a common appliance 200, while in other embodiments thecores 505 can be installed within one or more appliance(s) 200communicatively connected to one another. The cores 505 can in someembodiments comprise graphics processing software, while in otherembodiments the cores 505 provide general processing capabilities. Thecores 505 can be installed physically near each other and/or can becommunicatively connected to each other. The cores may be connected byany type and form of bus or subsystem physically and/or communicativelycoupled to the cores for transferring data between to, from and/orbetween the cores.

While each core 505 can comprise software for communicating with othercores, in some embodiments a core manager (not shown) can facilitatecommunication between each core 505. In some embodiments, the kernel mayprovide core management. The cores may interface or communicate witheach other using a variety of interface mechanisms. In some embodiments,core to core messaging may be used to communicate between cores, such asa first core sending a message or data to a second core via a bus orsubsystem connecting the cores. In some embodiments, cores maycommunicate via any type and form of shared memory interface. In oneembodiment, there may be one or more memory locations shared among allthe cores. In some embodiments, each core may have separate memorylocations shared with each other core. For example, a first core mayhave a first shared memory with a second core and a second share memorywith a third core. In some embodiments, cores may communicate via anytype of programming or API, such as function calls via the kernel. Insome embodiments, the operating system may recognize and supportmultiple core devices and provide interfaces and API for inter-corecommunications.

The flow distributor 550 can be any application, program, library,script, task, service, process or any type and form of executableinstructions executing on any type and form of hardware. In someembodiments, the flow distributor 550 may any design and construction ofcircuitry to perform any of the operations and functions describedherein. In some embodiments, the flow distributor distribute, forwards,routes, controls and/or manage the distribution of data packets amongthe cores 505 and/or packet engine or VIPs running on the cores. Theflow distributor 550, in some embodiments, can be referred to as aninterface master. In one embodiment, the flow distributor 550 comprisesa set of executable instructions executing on a core or processor of theappliance 200. In another embodiment, the flow distributor 550 comprisesa set of executable instructions executing on a computing machine incommunication with the appliance 200. In some embodiments, the flowdistributor 550 comprises a set of executable instructions executing ona NIC, such as firmware. In still other embodiments, the flowdistributor 550 comprises any combination of software and hardware todistribute data packets among cores or processors. In one embodiment,the flow distributor 550 executes on at least one of the cores 505A-N,while in other embodiments a separate flow distributor 550 assigned toeach core 505A-N executes on an associated core 505A-N. The flowdistributor may use any type and form of statistical or probabilisticalgorithms or decision making to balance the flows across the cores. Thehardware of the appliance, such as a NIC, or the kernel may be designedand constructed to support sequential operations across the NICs and/orcores.

In embodiments where the system 545 comprises one or more flowdistributors 550, each flow distributor 550 can be associated with aprocessor 505 or a packet engine 548. The flow distributors 550 cancomprise an interface mechanism that allows each flow distributor 550 tocommunicate with the other flow distributors 550 executing within thesystem 545. In one instance, the one or more flow distributors 550 candetermine how to balance load by communicating with each other. Thisprocess can operate substantially similarly to the process describedabove for submitting votes to an arbiter which then determines whichflow distributor 550 should receive the load. In other embodiments, afirst flow distributor 550′ can identify the load on an associated coreand determine whether to forward a first data packet to the associatedcore based on any of the following criteria: the load on the associatedcore is above a predetermined threshold; the load on the associated coreis below a predetermined threshold; the load on the associated core isless than the load on the other cores; or any other metric that can beused to determine where to forward data packets based in part on theamount of load on a processor.

The flow distributor 550 can distribute network traffic among the cores505 according to a distribution, computing or load balancing scheme suchas those described herein. In one embodiment, the flow distributor candistribute network traffic according to any one of a functionalparallelism distribution scheme 550, a data parallelism loaddistribution scheme 540, a flow-based data parallelism distributionscheme 520, or any combination of these distribution scheme or any loadbalancing scheme for distributing load among multiple processors. Theflow distributor 550 can therefore act as a load distributor by takingin data packets and distributing them across the processors according toan operative load balancing or distribution scheme. In one embodiment,the flow distributor 550 can comprise one or more operations, functionsor logic to determine how to distribute packers, work or loadaccordingly. In still other embodiments, the flow distributor 550 cancomprise one or more sub operations, functions or logic that canidentify a source address and a destination address associated with adata packet, and distribute packets accordingly.

In some embodiments, the flow distributor 550 can comprise areceive-side scaling (RSS) network driver, module 560 or any type andform of executable instructions which distribute data packets among theone or more cores 505. The RSS module 560 can comprise any combinationof hardware and software. In some embodiments, the RSS module 560 worksin conjunction with the flow distributor 550 to distribute data packetsacross the cores 505A-N or among multiple processors in amulti-processor network. The RSS module 560 can execute within the NIC552 in some embodiments, and in other embodiments can execute on any oneof the cores 505.

In some embodiments, the RSS module 560 uses the MICROSOFTreceive-side-scaling (RSS) scheme. In one embodiment, RSS is a MicrosoftScalable Networking initiative technology that enables receiveprocessing to be balanced across multiple processors in the system whilemaintaining in-order delivery of the data. The RSS may use any type andform of hashing scheme to determine a core or processor for processing anetwork packet.

The RSS module 560 can apply any type and form hash function such as theToeplitz hash function. The hash function may be applied to the hashtype or any the sequence of values. The hash function may be a securehash of any security level or is otherwise cryptographically secure. Thehash function may use a hash key. The size of the key is dependent uponthe hash function. For the Toeplitz hash, the size may be 40 bytes forIPv6 and 16 bytes for IPv4.

The hash function may be designed and constructed based on any one ormore criteria or design goals. In some embodiments, a hash function maybe used that provides an even distribution of hash result for differenthash inputs and different hash types, including TCP/IPv4, TCP/IPv6,IPv4, and IPv6 headers. In some embodiments, a hash function may be usedthat provides a hash result that is evenly distributed when a smallnumber of buckets are present (for example, two or four). In someembodiments, hash function may be used that provides a hash result thatis randomly distributed when a large number of buckets were present (forexample, 64 buckets). In some embodiments, the hash function isdetermined based on a level of computational or resource usage. In someembodiments, the hash function is determined based on ease or difficultyof implementing the hash in hardware. In some embodiments, the hashfunction is determined based on the ease or difficulty of a maliciousremote host to send packets that would all hash to the same bucket.

The RSS may generate hashes from any type and form of input, such as asequence of values. This sequence of values can include any portion ofthe network packet, such as any header, field or payload of networkpacket, or portions thereof. In some embodiments, the input to the hashmay be referred to as a hash type and include any tuples of informationassociated with a network packet or data flow, such as any of thefollowing: a four tuple comprising at least two IP addresses and twoports; a four tuple comprising any four sets of values; a six tuple; atwo tuple; and/or any other sequence of numbers or values. The followingare example of hash types that may be used by RSS:

4-tuple of source TCP Port, source IP version 4 (IPv4) address,destination TCP Port, and destination IPv4 address.

4-tuple of source TCP Port, source IP version 6 (IPv6) address,destination TCP Port, and destination IPv6 address.

2-tuple of source IPv4 address, and destination IPv4 address.

2-tuple of source IPv6 address, and destination IPv6 address.

2-tuple of source IPv6 address, and destination IPv6 address, includingsupport for parsing IPv6 extension headers.

The hash result or any portion thereof may be used to identify a core orentity, such as a packet engine or VIP, for distributing a networkpacket. In some embodiments, one or more hash bits or mask are appliedto the hash result. The hash bit or mask may be any number of bits orbytes. A NIC may support any number of bits, such as seven bits. Thenetwork stack may set the actual number of bits to be used duringinitialization. The number will be between 1 and 7, inclusive.

The hash result may be used to identify the core or entity via any typeand form of table, such as a bucket table or indirection table. In someembodiments, the number of hash-result bits are used to index into thetable. The range of the hash mask may effectively define the size of theindirection table. Any portion of the hash result or the hash resultitself may be used to index the indirection table. The values in thetable may identify any of the cores or processor, such as by a core orprocessor identifier. In some embodiments, all of the cores of themulti-core system are identified in the table. In other embodiments, aport of the cores of the multi-core system are identified in the table.The indirection table may comprise any number of buckets for example 2to 128 buckets that may be indexed by a hash mask. Each bucket maycomprise a range of index values that identify a core or processor. Insome embodiments, the flow controller and/or RSS module may rebalancethe network rebalance the network load by changing the indirectiontable.

In some embodiments, the multi-core system 575 does not include a RSSdriver or RSS module 560. In some of these embodiments, a softwaresteering module (not shown) or a software embodiment of the RSS modulewithin the system can operate in conjunction with or as part of the flowdistributor 550 to steer packets to cores 505 within the multi-coresystem 575.

The flow distributor 550, in some embodiments, executes within anymodule or program on the appliance 200, on any one of the cores 505 andon any one of the devices or components included within the multi-coresystem 575. In some embodiments, the flow distributor 550′ can executeon the first core 505A, while in other embodiments the flow distributor550″ can execute on the NIC 552. In still other embodiments, an instanceof the flow distributor 550′ can execute on each core 505 included inthe multi-core system 575. In this embodiment, each instance of the flowdistributor 550′ can communicate with other instances of the flowdistributor 550′ to forward packets back and forth across the cores 505.There exist situations where a response to a request packet may not beprocessed by the same core, i.e. the first core processes the requestwhile the second core processes the response. In these situations, theinstances of the flow distributor 550′ can intercept the packet andforward it to the desired or correct core 505, i.e. a flow distributorinstance 550′ can forward the response to the first core. Multipleinstances of the flow distributor 550′ can execute on any number ofcores 505 and any combination of cores 505.

The flow distributor may operate responsive to any one or more rules orpolicies. The rules may identify a core or packet processing engine toreceive a network packet, data or data flow. The rules may identify anytype and form of tuple information related to a network packet, such asa 4-tuple of source and destination IP address and source anddestination ports. Based on a received packet matching the tuplespecified by the rule, the flow distributor may forward the packet to acore or packet engine. In some embodiments, the packet is forwarded to acore via shared memory and/or core to core messaging.

Although FIG. 5B illustrates the flow distributor 550 as executingwithin the multi-core system 575, in some embodiments the flowdistributor 550 can execute on a computing device or appliance remotelylocated from the multi-core system 575. In such an embodiment, the flowdistributor 550 can communicate with the multi-core system 575 to takein data packets and distribute the packets across the one or more cores505. The flow distributor 550 can, in one embodiment, receive datapackets destined for the appliance 200, apply a distribution scheme tothe received data packets and distribute the data packets to the one ormore cores 505 of the multi-core system 575. In one embodiment, the flowdistributor 550 can be included in a router or other appliance such thatthe router can target particular cores 505 by altering meta dataassociated with each packet so that each packet is targeted towards asub-node of the multi-core system 575. In such an embodiment, CISCO'svn-tag mechanism can be used to alter or tag each packet with theappropriate meta data.

Illustrated in FIG. 5C is an embodiment of a multi-core system 575comprising one or more processing cores 505A-N. In brief overview, oneof the cores 505 can be designated as a control core 505A and can beused as a control plane 570 for the other cores 505. The other cores maybe secondary cores which operate in a data plane while the control coreprovides the control plane. The cores 505A-N may share a global cache580. While the control core provides a control plane, the other cores inthe multi-core system form or provide a data plane. These cores performdata processing functionality on network traffic while the controlprovides initialization, configuration and control of the multi-coresystem.

Further referring to FIG. 5C, and in more detail, the cores 505A-N aswell as the control core 505A can be any processor described herein.Furthermore, the cores 505A-N and the control core 505A can be anyprocessor able to function within the system 575 described in FIG. 5C.Still further, the cores 505A-N and the control core 505A can be anycore or group of cores described herein. The control core may be adifferent type of core or processor than the other cores. In someembodiments, the control may operate a different packet engine or have apacket engine configured differently than the packet engines of theother cores.

Any portion of the memory of each of the cores may be allocated to orused for a global cache that is shared by the cores. In brief overview,a predetermined percentage or predetermined amount of each of the memoryof each core may be used for the global cache. For example, 50% of eachmemory of each code may be dedicated or allocated to the shared globalcache. That is, in the illustrated embodiment, 2 GB of each coreexcluding the control plane core or core 1 may be used to form a 28 GBshared global cache. The configuration of the control plane such as viathe configuration services may determine the amount of memory used forthe shared global cache. In some embodiments, each core may provide adifferent amount of memory for use by the global cache. In otherembodiments, any one core may not provide any memory or use the globalcache. In some embodiments, any of the cores may also have a local cachein memory not allocated to the global shared memory. Each of the coresmay store any portion of network traffic to the global shared cache.Each of the cores may check the cache for any content to use in arequest or response. Any of the cores may obtain content from the globalshared cache to use in a data flow, request or response.

The global cache 580 can be any type and form of memory or storageelement, such as any memory or storage element described herein. In someembodiments, the cores 505 may have access to a predetermined amount ofmemory (i.e. 32 GB or any other memory amount commensurate with thesystem 575). The global cache 580 can be allocated from thatpredetermined amount of memory while the rest of the available memorycan be allocated among the cores 505. In other embodiments, each core505 can have a predetermined amount of memory. The global cache 580 cancomprise an amount of the memory allocated to each core 505. This memoryamount can be measured in bytes, or can be measured as a percentage ofthe memory allocated to each core 505. Thus, the global cache 580 cancomprise 1 GB of memory from the memory associated with each core 505,or can comprise 20 percent or one-half of the memory associated witheach core 505. In some embodiments, only a portion of the cores 505provide memory to the global cache 580, while in other embodiments theglobal cache 580 can comprise memory not allocated to the cores 505.

Each core 505 can use the global cache 580 to store network traffic orcache data. In some embodiments, the packet engines of the core use theglobal cache to cache and use data stored by the plurality of packetengines. For example, the cache manager of FIG. 2A and cachefunctionality of FIG. 2B may use the global cache to share data foracceleration. For example, each of the packet engines may storeresponses, such as HTML data, to the global cache. Any of the cachemanagers operating on a core may access the global cache to servercaches responses to client requests.

In some embodiments, the cores 505 can use the global cache 580 to storea port allocation table which can be used to determine data flow basedin part on ports. In other embodiments, the cores 505 can use the globalcache 580 to store an address lookup table or any other table or listthat can be used by the flow distributor to determine where to directincoming and outgoing data packets. The cores 505 can, in someembodiments read from and write to cache 580, while in other embodimentsthe cores 505 can only read from or write to cache 580. The cores mayuse the global cache to perform core to core communications.

The global cache 580 may be sectioned into individual memory sectionswhere each section can be dedicated to a particular core 505. In oneembodiment, the control core 505A can receive a greater amount ofavailable cache, while the other cores 505 can receiving varying amountsor access to the global cache 580.

In some embodiments, the system 575 can comprise a control core 505A.While FIG. 5C illustrates core 1 505A as the control core, the controlcore can be any core within the appliance 200 or multi-core system.Further, while only a single control core is depicted, the system 575can comprise one or more control cores each having a level of controlover the system. In some embodiments, one or more control cores can eachcontrol a particular aspect of the system 575. For example, one core cancontrol deciding which distribution scheme to use, while another corecan determine the size of the global cache 580.

The control plane of the multi-core system may be the designation andconfiguration of a core as the dedicated management core or as a mastercore. This control plane core may provide control, management andcoordination of operation and functionality the plurality of cores inthe multi-core system. This control plane core may provide control,management and coordination of allocation and use of memory of thesystem among the plurality of cores in the multi-core system, includinginitialization and configuration of the same. In some embodiments, thecontrol plane includes the flow distributor for controlling theassignment of data flows to cores and the distribution of networkpackets to cores based on data flows. In some embodiments, the controlplane core runs a packet engine and in other embodiments, the controlplane core is dedicated to management and control of the other cores ofthe system.

The control core 505A can exercise a level of control over the othercores 505 such as determining how much memory should be allocated toeach core 505 or determining which core 505 should be assigned to handlea particular function or hardware/software entity. The control core505A, in some embodiments, can exercise control over those cores 505within the control plan 570. Thus, there can exist processors outside ofthe control plane 570 which are not controlled by the control core 505A.Determining the boundaries of the control plane 570 can includemaintaining, by the control core 505A or agent executing within thesystem 575, a list of those cores 505 controlled by the control core505A. The control core 505A can control any of the following:initialization of a core; determining when a core is unavailable;re-distributing load to other cores 505 when one core fails; determiningwhich distribution scheme to implement; determining which core shouldreceive network traffic; determining how much cache should be allocatedto each core; determining whether to assign a particular function orelement to a particular core; determining whether to permit cores tocommunicate with one another; determining the size of the global cache580; and any other determination of a function, configuration oroperation of the cores within the system 575.

F. Systems and Methods for Providing a Distributed Cluster Architecture

As discussed in the previous section, to overcome limitations ontransistor spacing and CPU speed increases, many CPU manufacturers haveincorporated multi-core CPUs to improve performance beyond that capableof even a single, higher speed CPU. Similar or further performance gainsmay be made by operating a plurality of appliances, either single ormulti-core, together as a distributed or clustered appliance. Individualcomputing devices or appliances may be referred to as nodes of thecluster. A centralized management system may perform load balancing,distribution, configuration, or other tasks to allow the nodes tooperate in conjunction as a single computing system. Externally or toother devices, including servers and clients, in many embodiments, thecluster may be viewed as a single virtual appliance or computing device,albeit one with performance exceeding that of a typical individualappliance.

Referring now to FIG. 6, illustrated is an embodiment of a computingdevice cluster or appliance cluster 600. A plurality of appliances 200a-200 n or other computing devices, sometimes referred to as nodes, suchas desktop computers, servers, rack mount servers, blade servers, or anyother type and form of computing device may be joined into a singleappliance cluster 600. Although referred to as an appliance cluster, inmany embodiments, the cluster may operate as an application server,network storage server, backup service, or any other type of computingdevice without limitation. In many embodiments, the appliance cluster600 may be used to perform many of the functions of appliances 200, WANoptimization devices, network acceleration devices, or other devicesdiscussed above.

In some embodiments, the appliance cluster 600 may comprise a homogenousset of computing devices, such as identical appliances, blade serverswithin one or more chassis, desktop or rack mount computing devices, orother devices. In other embodiments, the appliance cluster 600 maycomprise a heterogeneous or mixed set of devices, including differentmodels of appliances, mixed appliances and servers, or any other set ofcomputing devices. This may allow for an appliance cluster 600 to beexpanded or upgraded over time with new models or devices, for example.

In some embodiments, each computing device or appliance 200 of anappliance cluster 600 may comprise a multi-core appliance, as discussedabove. In many such embodiments, the core management and flowdistribution methods discussed above may be utilized by each individualappliance, in addition to the node management and distribution methodsdiscussed herein. This may be thought of as a two-tier distributedsystem, with one appliance comprising and distributing data to multiplenodes, and each node comprising and distributing data for processing tomultiple cores. Accordingly, in such embodiments, the node distributionsystem need not manage flow distribution to individual cores, as thatmay be taken care of by a master or control core as discussed above.

In many embodiments, an appliance cluster 600 may be physically grouped,such as a plurality of blade servers in a chassis or plurality of rackmount devices in a single rack, but in other embodiments, the appliancecluster 600 may be distributed in a plurality of chassis, plurality ofracks, plurality of rooms in a data center, plurality of data centers,or any other physical arrangement. Accordingly, the appliance cluster600 may be considered a virtual appliance, grouped via commonconfiguration, management, and purpose, rather than a physical group.

In some embodiments, an appliance cluster 600 may be connected to one ormore networks 104, 104′. For example, referring briefly back to FIG. 1A,in some embodiments, an appliance 200 may be deployed between a network104 joined to one or more clients 102, and a network 104′ joined to oneor more servers 106. An appliance cluster 600 may be similarly deployedto operate as a single appliance. In many embodiments, this may notrequire any network topology changes external to appliance cluster 600,allowing for ease of installation and scalability from a singleappliance scenario. In other embodiments, an appliance cluster 600 maybe similarly deployed as shown in FIGS. 1B-1D or discussed above. Instill other embodiments, an appliance cluster may comprise a pluralityof virtual machines or processes executed by one or more servers. Forexample, in one such embodiment, a server farm may execute a pluralityof virtual machines, each virtual machine configured as an appliance200, and a plurality of the virtual machines acting in concert as anappliance cluster 600. In yet still other embodiments, an appliancecluster 600 may comprise a mix of appliances 200 or virtual machinesconfigured as appliances 200. In some embodiments, appliance cluster 600may be geographically distributed, with the plurality of appliances 200not co-located. For example, referring back to FIG. 6, in one suchembodiment, a first appliance 200 a may be located at a first site, suchas a data center and a second appliance 200 b may be located at a secondsite, such as a central office or corporate headquarters. In a furtherembodiment, such geographically remote appliances may be joined by adedicated network, such as a T1 or T3 point-to-point connection; a VPN;or any other type and form of network. Accordingly, although there maybe additional communications latency compared to co-located appliances200 a-200 b, there may be advantages in reliability in case of sitepower failures or communications outages, scalability, or otherbenefits. In some embodiments, latency issues may be reduced throughgeographic or network-based distribution of data flows. For example,although configured as an appliance cluster 600, communications fromclients and servers at the corporate headquarters may be directed to theappliance 200 b deployed at the site, load balancing may be weighted bylocation, or similar steps can be taken to mitigate any latency.

Still referring to FIG. 6, an appliance cluster 600 may be connected toa network via a client data plane 602. In some embodiments, client dataplane 602 may comprise a communication network, such as a network 104,carrying data between clients and appliance cluster 600. In someembodiments, client data plane 602 may comprise a switch, hub, router,or other network devices bridging an external network 104 and theplurality of appliances 200 a-200 n of the appliance cluster 600. Forexample, in one such embodiment, a router may be connected to anexternal network 104, and connected to a network interface of eachappliance 200 a-200 n. In some embodiments, this router or switch may bereferred to as an interface manager, and may further be configured todistribute traffic evenly across the nodes in the application cluster600. Thus, in many embodiments, the interface master may comprise a flowdistributor external to appliance cluster 600. In other embodiments, theinterface master may comprise one of appliances 200 a-200 n. Forexample, a first appliance 200 a may serve as the interface master,receiving incoming traffic for the appliance cluster 600 anddistributing the traffic across each of appliances 200 b-200 n. In someembodiments, return traffic may similarly flow from each of appliances200 b-200 n via the first appliance 200 a serving as the interfacemaster. In other embodiments, return traffic from each of appliances 200b-200 n may be transmitted directly to a network 104, 104′, or via anexternal router, switch, or other device. In some embodiments,appliances 200 of the appliance cluster not serving as an interfacemaster may be referred to as interface slaves 610A-610N.

The interface master may perform load balancing or traffic flowdistribution in any of a variety of ways. For example, in someembodiments, the interface master may comprise a router performingequal-cost multi-path (ECMP) routing with next hops configured withappliances or nodes of the cluster. The interface master may use anopen-shortest path first (OSPF) In some embodiments, the interfacemaster may use a stateless hash-based mechanism for trafficdistribution, such as hashes based on IP address or other packetinformation tuples, as discussed above. Hash keys and/or salt may beselected for even distribution across the nodes. In other embodiments,the interface master may perform flow distribution via link aggregation(LAG) protocols, or any other type and form of flow distribution, loadbalancing, and routing.

In some embodiments, the appliance cluster 600 may be connected to anetwork via a server data plane 604. Similar to client data plane 602,server data plane 604 may comprise a communication network, such as anetwork 104′, carrying data between servers and appliance cluster 600.In some embodiments, server data plane 604 may comprise a switch, hub,router, or other network devices bridging an external network 104′ andthe plurality of appliances 200 a-200 n of the appliance cluster 600.For example, in one such embodiment, a router may be connected to anexternal network 104′, and connected to a network interface of eachappliance 200 a-200 n. In many embodiments, each appliance 200 a-200 nmay comprise multiple network interfaces, with a first network interfaceconnected to client data plane 602 and a second network interfaceconnected to server data plane 604. This may provide additional securityand prevent direct interface of client and server networks by havingappliance cluster 600 server as an intermediary device. In otherembodiments, client data plane 602 and server data plane 604 may bemerged or combined. For example, appliance cluster 600 may be deployedas a non-intermediary node on a network with clients 102 and servers106. As discussed above, in many embodiments, an interface master may bedeployed on the server data plane 604, for routing and distributingcommunications from the servers and network 104′ to each appliance ofthe appliance cluster. In many embodiments, an interface master forclient data plane 602 and an interface master for server data plane 604may be similarly configured, performing ECMP or LAG protocols asdiscussed above.

In some embodiments, each appliance 200 a-200 n in appliance cluster 600may be connected via an internal communication network or back plane606. Back plane 606 may comprise a communication network for inter-nodeor inter-appliance control and configuration messages, and forinter-node forwarding of traffic. For example, in one embodiment inwhich a first appliance 200 a communicates with a client via network104, and a second appliance 200 b communicates with a server via network104′, communications between the client and server may flow from clientto first appliance, from first appliance to second appliance via backplane 606, and from second appliance to server, and vice versa. In otherembodiments, back plane 606 may carry configuration messages, such asinterface pause or reset commands; policy updates such as filtering orcompression policies; status messages such as buffer status, throughput,or error messages; or any other type and form of inter-nodecommunication. In some embodiments, RSS keys or hash keys may be sharedby all nodes in the cluster, and may be communicated via back plane 606.For example, a first node or master node may select an RSS key, such asat startup or boot, and may distribute this key for use by other nodes.In some embodiments, back plane 606 may comprise a network betweennetwork interfaces of each appliance 200, and may comprise a router,switch, or other network device (not illustrated). Thus, in someembodiments and as discussed above, a router for client data plane 602may be deployed between appliance cluster 600 and network 104, a routerfor server data plane 604 may be deployed between appliance cluster 600and network 104′, and a router for back plane 606 may be deployed aspart of appliance cluster 600. Each router may connect to a differentnetwork interface of each appliance 200. In other embodiments, one ormore planes 602-606 may be combined, or a router or switch may be splitinto multiple LANs or VLANs to connect to different interfaces ofappliances 200 a-200 n and serve multiple routing functionssimultaneously, to reduce complexity or eliminate extra devices from thesystem.

In some embodiments, a control plane (not illustrated) may communicateconfiguration and control traffic from an administrator or user to theappliance cluster 600. In some embodiments, the control plane may be afourth physical network, while in other embodiments, the control planemay comprise a VPN, tunnel, or communication via one of planes 602-606.Thus, the control plane may, in some embodiments, be considered avirtual communication plane. In other embodiments, an administrator mayprovide configuration and control through a separate interface, such asa serial communication interface such as RS-232; a USB communicationinterface; or any other type and form of communication. In someembodiments, an appliance 200 may comprise an interface foradministration, such as a front panel with buttons and a display; a webserver for configuration via network 104, 104′ or back plane 606; or anyother type and form of interface.

In some embodiments, as discussed above, appliance cluster 600 mayinclude internal flow distribution. For example, this may be done toallow nodes to join/leave transparently to external devices. To preventan external flow distributor from needing to be repeatedly reconfiguredon such changes, a node or appliance may act as an interface master ordistributor for steering network packets to the correct node within thecluster 600. For example, in some embodiments, when a node leaves thecluster (such as on failure, reset, or similar cases), an external ECMProuter may identify the change in nodes, and may rehash all flows toredistribute traffic. This may result in dropping and resetting allconnections. The same drop and reset may occur when the node rejoins. Insome embodiments, for reliability, two appliances or nodes withinappliance cluster 600 may receive communications from external routersvia connection mirroring.

In many embodiments, flow distribution among nodes of appliance cluster600 may use any of the methods discussed above for flow distributionamong cores of an appliance. For example, in one embodiment, a masterappliance, master node, or interface master, may compute a RSS hash,such as a Toeplitz hash on incoming traffic and consult a preferencelist or distribution table for the hash. In many embodiments, the flowdistributor may provide the hash to the recipient appliance whenforwarding the traffic. This may eliminate the need for the node torecompute the hash for flow distribution to a core. In many suchembodiments, the RSS key used for calculating hashes for distributionamong the appliances may comprise the same key as that used forcalculating hashes for distribution among the cores, which may bereferred to as a global RSS key, allowing for reuse of the calculatedhash. In some embodiments, the hash may be computed with input tuples oftransport layer headers including port numbers, internet layer headersincluding IP addresses; or any other packet header information. In someembodiments, packet body information may be utilized for the hash. Forexample, in one embodiment in which traffic of one protocol isencapsulated within traffic of another protocol, such as lossy UDPtraffic encapsulated via a lossless TCP header, the flow distributor maycalculate the hash based on the headers of the encapsulated protocol(e.g. UDP headers) rather than the encapsulating protocol (e.g. TCPheaders). Similarly, in some embodiments in which packets areencapsulated and encrypted or compressed, the flow distributor maycalculate the hash based on the headers of the payload packet afterdecryption or decompression. In still other embodiments, nodes may haveinternal IP addresses, such as for configuration or administrationpurposes. Traffic to these IP addresses need not be hashed anddistributed, but rather may be forwarded to the node owning thedestination address. For example, an appliance may have a web server orother server running for configuration or administration purposes at anIP address of 1.2.3.4, and, in some embodiments, may register thisaddress with the flow distributor as its internal IP address. In otherembodiments, the flow distributor may assign internal IP addresses toeach node within the appliance cluster 600. Traffic arriving fromexternal clients or servers, such as a workstation used by anadministrator, directed to the internal IP address of the appliance(1.2.3.4) may be forwarded directly, without requiring hashing.

G. Systems and Methods for Maintaining a Session Via an IntermediaryDevice

The present disclosure is directed towards systems and methods formaintaining a session via an intermediary device. In particular, thepresent solution relates to systems and methods for resuming anapplication session with a large, dynamic state maintained in a standbyintermediary device when the primary device fails. An intermediarydevice can refer to an active-standby appliance pair (or intermediaryappliance pair) that includes a first intermediary device (or firstdevice) and a second intermediary device (or second device). The firstdevice can be in an active mode in which the first device activelyservices requests from a client by parsing packets received from theclient, providing the client with response packets received from theserver, or otherwise providing the client with access to an applicationexecuted by a server. In some cases, the first device of theintermediary appliance pair that is initially configured to be in theactive mode can be referred to as the primary device. The intermediaryappliance pair can include a second device that is initially configuredto be in standby mode. The second device may not actively servicerequests from the client device. The second device may be referred to asthe secondary device because it is in standby mode and does not activelyservice requests received from the client or provide responses receivedfrom the server to the client. If the primary device fails, becomesunresponsive, is brought down for scheduled maintenance or is otherwiseunable to process requests received from the client device, forwardresponses received from the server, or otherwise provide the clientdevice with suitable access to the application executed by the serversuch that the client device can interact with the application, thesecondary device can become the new primary device and service theclient device by processing client requests.

An intermediary device can be configured to perform deep packetinspection on the application network traffic. The application trafficcan refer to packets received from the client that are to be processedor provided to the server, or packets received from the server that areto be processed or provided to the client. The intermediary device canperform deep packet inspection to gain visibility into the session stateor to facilitate troubleshooting or identify problems or issues. In sucha deployment, if the primary device fails and the secondary devicebecomes the new primary device, the client device accessing theapplication or desktop session over an application server protocol(e.g., Independent Computing Architecture “ICA”) may be disconnectedfrom the session. The client device may have to then re-login to thesession to access the application or desktop session provided by theserver via the intermediary device.

Systems and methods of the present solution can seamlessly resume theaffected session on the new primary intermediary device. By seamlesslyresuming the affected session on the new primary intermediary device,client device may be unaffected by the failure of the original primaryintermediary device causing the standby secondary to become the newprimary.

For example, computing network can provide high availability ofapplication resources using a network intermediary device (e.g.,NetScaler® manufactured by Citrix Systems, Inc. of Ft. Lauderdale, Fla.)that is deployed in an active-standby appliance pair. In anactive-standby appliance pair, a first intermediary device activelyservices client device, while a second intermediary device is maintainedin a standby mode. For example, and in some embodiments, a firstintermediary device can be in an active mode and can parse and processan application session such as an ICA session. The first intermediarydevice can be paired with a second intermediary device that ismaintained in a standby mode. The first intermediary device can maintainsignificant state information, which may be dynamic and change on aper-packet basis (e.g., as each packet is being processed). If the firstintermediary device fails, then the standby device can become the newprimary device. The secondary device can become the new primary deviceand resume the session without affecting the user experience provided bythe client device.

The intermediary appliance pair (e.g., the first intermediary device andsecond intermediary device) can be configured to provide visibility intothe session between the client device and the server providing theapplication. For example, the intermediary appliance pair can providevisibility into the protocol (e.g., an ICA protocol, or a highdefinition experience “HDX” protocol) for troubleshooting or analyticspurposes. To parse the protocol, the appliance pair manages a largeamount of state information within the device. This state informationcan include, e.g., information arising out of parsing an ICA protocol,parsing a common gateway protocol (“CGP”), decrypting and re-encryptingICA frames, or decompressing ICA Frames. As a result, the stateinformation maintained by the intermediary device may be very large(e.g., 5 megabytes, 50 megabytes, 100 megabytes, 500 megabytes, or 1gigabyte), and this state information can change with one or morepackets processed by the intermediary appliance pair (e.g., can changewith every packet processed).

The primary intermediary device can maintain the state per session inmemory of the primary intermediary device. Because of the size of thestate that is updated on every packet, it may be challenging or notpossible for the primary intermediary device to share the state with orupdate the state in an external device (e.g. another intermediarydevice). If the primary intermediary device cannot share the state withor update the state in an external device, the state maintained inmemory of the primary intermediary device may be lost when the primaryintermediary device goes offline. As the primary intermediary devicegoes offline, connections of the primary intermediary device (e.g.,transmission control protocol “TCP” connections) can be reset. Whenconnections between the client device and the primary intermediarydevice are reset, an agent executing on the client device may initiate asession reconnect. The new connection (e.g., TCP connection) establishedvia the session reconnect initiated by the agent of the client devicecan land on or be established via the new primary intermediary device(e.g., the second intermediary device that was previously in standbymode). If this new primary intermediary device does not have stateinformation for the session, the new primary intermediary may not beable to resume the session. Systems and methods of the present solutioncan allow the second intermediary device (or secondary device) tomaintain state on the second device while in standby mode in tandem withthe primary intermediary device. Thus, when the primary intermediarydevice goes offline and the secondary intermediary device takes over inthe new primary role, the secondary device can support and continue onwith the session reconnect initiated by the client agent.

In some embodiments, the primary intermediary device and the secondaryintermediary device can both be in a ready state. A ready state canindicate that a device is ready to parse packets that carry applicationprotocol data and application session metadata. During applicationlaunch, an agent executing on a client device can initiate a request toconnect via a protocol connection to a backend server or host via aprimary intermediary device. The primary intermediary device can detectthe request to initiate the connection and launch the applicationcorrespond to a new protocol connection, and the primary intermediarydevice can parse and process the request.

While the primary intermediary device parses and processes the requestor other data packets from the agent executing on the client device, theprimary intermediary device can detect that a secondary intermediarydevice is in the ready state. Responsive to detecting that the secondaryintermediary device is in the ready state, the primary intermediarydevice can mark the session in an update state and also forwardapplication protocol data and the application session metadatacorresponding to the request or the data packets to the secondaryintermediary device. The application protocol data and applicationsession meta data can be collectively referred to as application data.The application protocol data can refer to a high definition experience(“HDX”) protocol data. Application session data can refer to an HDXsession meta data. The secondary intermediary can receive theapplication data and parse the application data, or application protocoldata or application session meta data thereof.

Thus, by forwarding the application data from the primary device to thesecondary device and instructing the secondary device to parse the sameapplication protocol data as the primary intermediary device, systemsand methods of the present solution can maintain the same session statein both the primary intermediary device and the secondary intermediarydevice. By maintaining the same session state in both the primary andsecondary intermediary devices, the secondary intermediary device canseamlessly take over when the primary intermediary device fails orotherwise becomes unresponsive. For example, when the primaryintermediary device fails, all TCP connections can be reset. The agentexecuting on the client device sends a request to establish a newCGP/ICA connection via a session reconnect process. The new connectioncan land on the new primary intermediary device (e.g., the formersecondary intermediary device in standby mode). The new primaryintermediary device can inspects, process, or analyze the sessionreconnect connection to identify and retrieve the session stateinformation associated with this session reconnect. This session stateinformation may have been created and maintained by the new primarydevice when the new primary device was the secondary intermediary devicevia packet replay from the previous (e.g., original or initial) primaryintermediary device.

If, at some point in this process, the original primary intermediarydevice determines or detects that the secondary intermediary device(e.g., the standby device) is not in ready state (e.g., due to failureof the secondary intermediary, the secondary intermediary device beingunresponsive or offline due to scheduled or unscheduled maintenance),the primary intermediary device can mark the session in a down state ornot ready state. When the primary intermediary device marks the sessionin the down state, the primary intermediary device can stop, block,prevent, or cease forwarding the application protocol data orapplication session meta data to the secondary intermediary device.Thus, if the session in the down state, the primary intermediary devicedoes not forward application data to the secondary intermediary device.

If, at some later time, the primary intermediary device detects that thesecondary intermediary device is back online or back in a ready stateindicating that the secondary intermediary device is ready to parseapplication protocol data to maintain a session state in memory of thesecondary intermediary device, the primary intermediary device can markthe session in a session update state. Responsive to a transition of thesession state from the down state to the update state, the primaryintermediary device can push, provide, transfer, or otherwise forwardthe application protocol session state to the secondary intermediarydevice so as to bring the secondary intermediary device up-to-date. Forexample, the primary secondary device can push the complete applicationprotocol session state to the secondary intermediary device to bring thesecondary intermediary device up-to-date in a single communication.Thereafter, once the secondary intermediary device maintains a sessionstate in memory of the secondary intermediary device that matches thesession state in the primary intermediary device, the primaryintermediary device can continue to forward or replay application datato the secondary intermediary device to synchronize the session statemaintained by the secondary intermediary device in with the sessionstate of the primary intermediary device.

Now referring now to FIG. 7A, a block diagram of an embodiment of asystem for maintaining a session is shown. The system 700 includes anactive-standby appliance pair 740 that includes a first intermediarydevices 200 a and a second intermediary device 200 b. In some cases, theactive-standby appliance pair 740 can be referred to as an appliancepair 740, appliance pair 740, intermediary appliance pair 740, or device740. The appliance pair 740 can include one or more functionality orcomponent of application cluster 600 depicted in FIG. 6. The firstdevice 200 a of the active-standby pair 740 can be referred to as afirst intermediary device 200 a, primary intermediary device 200 a,primary device 200 a, initial primary device 200 a, or original primarydevice 200 a. The second device 200 b of the active-standby pair 740 canbe referred to as a second intermediary device 200 b, secondaryintermediary device 200 b, second device 200 b, initial standby device200 b, and new primary device 200 b. The intermediary devices 200 a and200 b, or appliance pair 740, is intermediary to a plurality of servers106 a-n and to a plurality of clients 102 a-n. The appliances 200 a and200 b can manage or optimize the delivery of website content, services,resources or applications provided via the servers 106 a-n over thenetwork 104 or network 104′, by providing application-level security,optimization, or traffic management. The client 102 may include one ormore component or functionality of client 102. The server 106 mayinclude one or more component or functionality of server 106. Theintermediary devices 200 a and 200 b may be the same or similar to theappliance 200 described above with respect to FIGS. 1-6, or include oneor more functionality or components thereof. The appliance pair 740 maybe the same or similar to the appliance cluster 600 described above withrespect to FIGS. 1-6, or include one or more functionality or componentsthereof. In some embodiments, the clients 102 a-n are the same orsimilar to the clients 102 a-n and the servers 106 a-n are the same orsimilar to the servers 106 a-n as described above with respect to FIGS.1-6, or include one or more functionality or components thereof. In someembodiments, the clients 102 and servers 106 of system 700 are furtherconfigured to perform functions or provide features for authenticating aclient.

Still referring to FIG. 7A, and in further detail, the appliance pair740 includes an interface 705. The interface 705 can include anapplication programming interface, a graphical user interface,communication ports, or be configured with one or more communication ornetworking protocols, such as TCP/IP, etc. The interface 705 can beconfigured to receive or intercept data packets, receive data packets,monitor network traffic, or otherwise obtain or transmit/conveyinformation via network 104 or network 104′.

In some embodiments, the interface 705 receives a request from a client102 a of the plurality of clients 102 a-n. The interface 705 may receivethe request via a networking protocol, communication protocol,application layer protocol, transport protocol, or encryption protocol.Protocols can include, e.g., HTTP, TCP, ICA, or HDX. The protocol can bea stateful protocol or a stateless protocol. The request may includeinformation about the client or the resource to which the client 102 ais requesting access. In some embodiments, the resource provided byserver 106 a-n may be a secure resource for which a client or user ofthe client device may require authentication, authorization or approvalbefore access is granted.

In some embodiments, the appliance pair 740 can include the interface705 designed and constructed to receive network communications from oneor more clients 102 a-n. The interface 705 may be the same or similar tothe interfaces 608 or 610 a-n described above with respect to FIGS. 1-6,or include one or more functionality or components thereof. Theinterface 705 can receive data packets from a client 102 a, such as viaclient agent 120 a. The interface 705 can forward or relay the datapackets received from client 102 a to the first device 200 a. Forexample, the interface 705 can be configured to automatically forwarddata packets received from a client agent 120 a to the first device 200a. The interface 705 can be further configured to forward or relay thedata packets to the primary device 200 a. The primary device 200 a canrefer to the intermediary device of the active-standby intermediaryappliance pair 740 that is currently in the active mode. Thus, theinterface 705 can determine which of the intermediary devices 200 a and200 b is currently the primary device configured to actively servicerequests from client agent 120, and forward the requests to the primarydevice.

To determine which one of the intermediary devices 200 a-b is currentlythe primary device, the interface 705 can maintain, in memory,information about the role of an intermediary device 200 a-b. Forexample, the interface 705 can poll one or more of intermediary devices200 a and 200 b and identify, determine, or receive an indication as towhich device is the active, primary device. The interface 705 can storethat indication in a role data structure in memory of the interface 705.The interface 705 can poll intermediary devices 200 a-b based on a timeinterval, such as every second, 5 seconds, 10 seconds, 60 seconds, 5minutes, or 10 minutes. In another example, the interface 705 may pollthe intermediary devices 200 a-b responsive to an event, condition ortrigger. For example, the interface 705 may attempt to forward a packetfrom the client agent 120 to intermediary device 200 a, but may discoverthat intermediary device 200 a is offline or otherwise unresponsive. Theinterface 705 can update the role data structure in memory of theinterface 705 with the update information. In response to determiningthat intermediary device 200 a is offline or unresponsive, the interface705 can forward the received data packet to the second intermediarydevice 200 b, which can act as the new primary device 200 b.

The first intermediary device 200 a and the second intermediary device200 b can include one or more component or functionality of appliance200. The first intermediary device 200 a can include a monitor 710 a, apacket engine 715 a, and a data repository 720 a. The data repository720 a can include or store session data 725 a, mode information 730 aand a parameter 735 a. The second intermediary device 200 b can includea monitor 710 b, a packet engine 715 b, and a data repository 720 b. Thedata repository 720 b can include or store session data 725 b, modeinformation 730 b and a parameter 735 b. The monitor 710 a can includedigital circuitry, hardware, one or more processors, memory or softwaredesigned, constructed and configured to detect or determine a sessionstate, determine a device state, determine a device mode, or update astate or mode. The packet engines 715 a-b can include digital circuitry,hardware, one or more processors, memory or software designed,constructed and configured to parse or process data packets. The packetengines 715 a-b may be the same or similar to the packet engine 240described above with respect to FIGS. 1-6, or include one or morefunctionality or components thereof.

Each device 200 a-b can be associated with or correspond to a devicemode or mode. The mode of a device 200 a-b can be one of active orstandby. The mode can change over time or during a session. Active modecan refer to a mode in which the device 200 a actively services theclient 102 by parsing and processing requests or data packets receivedfrom the client or client agent 120 thereof. In the active mode, thedevice 200 a receives data packets from client 102, parses and processesthe packets, and forwards data corresponding to the processed packets toa corresponding server 106 a-n. In the active mode, the device canmaintain a session state in memory of the device. Thereafter, the device200 a in the active mode can receive a response from the server 106,parse and process the response, and forward data corresponding to theresponse to the same client 102.

In the standby mode, the device, such as device 200 b can receive datacorresponding to the data packets received from the client and parse andprocess the data to maintain a session state in memory of the device 200b. In the standby mode, the device 200 b can maintain the same sessionstate as the session state maintained in memory of the device in theactive mode, such as device 200 a. However, while in the standby mode,the device 200 b may not actively service client requests by respondingto the client request or sending requests to a server 106.

The first device 200 a in the active mode can be communicatively coupledwith or interfaced with the second device 200 b in the standby mode. Thefirst and second devices 200 a-b can store mode information in acorresponding mode data structure 730 a-b. For example, the first device200 a can include a data repository 720 a or memory location 720 a thatincludes a mode data structure 730 a. The mode data structure 730 a caninclude a data field or parameter field for the mode. The parameterfield can store a value for the mode, such as active or standby. Theparameter field can include other values, terms, characters, symbols,strings, or binary indicators that can indicate whether a device is inthe active mode or standby mode. For example, terms functional, inoperation, or service can indicate the active mode. For example, termspassive, waiting, or backup can indicate that the device is in thestandby mode.

The monitor 710 a can be configured to determine whether a device 200a-b is in a ready state or a not ready (or unready) state. A ready statecan refer to a state of a device that indicates that the device is readyto parse data corresponding to data packets in order to maintain, inmemory of the device, a state of the session with the client device. Theready state can be different from the active mode. For example, a devicein the standby mode can be in the ready state. When the device is in thestandby mode and the ready state, the device may not actively serviceclient requests, but may still maintain the session state in memory ofthe device. For example, the device in the standby mode and ready statecan receive application protocol data and application session metadatato maintain, in memory of the device, the same state of the applicationaccessed via the session provided by a device in the active mode.

To determine whether a device is in the ready state, the monitor 710 canpoll the device. For example, monitor 710 a of the first device 200 acan poll the second device 200 b with a status request. In responsive toreceiving the request, the second device 200 b can respond to therequest with a status update. For example, the monitor 710 b of thesecond device 200 b can determine whether the second device isoperational or able to parse or process data packets to maintain asession state. The monitor 710 b can initiate or execute a diagnosticroutine or test routine that checks system components to confirm whetherthey are operational or properly configured to maintain a session state.The monitor 710 b can further determine whether the second device 200 bcould resume the session with the client should the first device 200 ago offline. For example, the monitor 710 b can determine that one ormore hardware or software components of the second device 200 b arefunctioning and meet predetermined criteria, thresholds, or statuschecks. Thus, the monitor 710 b can determine that the second device 200b is in a ready state, and transmit an indication of the ready state tothe first device 200 a. The first device 200 a (e.g., via monitor 710 a)can receive the indication to detect that the second device 200 b is inthe ready state.

In some embodiments, the first device 200 a can detect that the seconddevice 200 b is in the ready state by performing a handshaking routine,based on a response time, or using a configuration file storing stateinformation. For example, the appliance pair 740 can include, access,retrieve or maintain a configuration file in a data repository thatincludes a field storing a value that indicates whether a device is inthe ready state or unready or not ready state. The indication of a readystate or not ready state can include other values, terms, characters,symbols, strings, or binary indicators that can indicate whether adevice is in the ready state or not ready state.

Upon determining whether the second device 200 b is in a ready state ornot ready state, the monitor 710 a can mark a session state of thesession with the client 102. The monitor 710 can mark the session statewith one or more indicators, including, e.g., update state or downstate. The update state can refer to a state in which the first deviceforwards or replays data corresponding to the data packets received fromthe client to the second device 200 b. Replaying a data packet can referto re-transmitting some or all the information of the received datapacket. For example, the first device 200 a can replay the applicationprotocol data to the second device 200 b by transmitting the applicationprotocol data received from the client device to the second device. Thefirst device 200 a can cache the application protocol data and send thecached version of the application protocol data, or otherwise forward orreplay the application data to the second device 200 b. The down statecan refer to a state in which the first device does 200 a not forward orreplay data corresponding to the data packets received from the clientto the second device 200 b.

The monitor 710 a of the first device 200 a (which is in the activemode) can mark the session state with the update state or the down stateresponsive to determining or detecting whether the second device 200 b(which is in the standby mode) is in the ready state or not ready state.If the second device 200 b is in the ready state, the monitor 710 amarks the session state with the update state. If the second device 200b is not ready or in the unready or not ready state, the monitor 710 amarks the session state with the down state.

The monitor 710 a can mark the session state with the update state orthe down state by setting a value of a parameter stored in the datarepository 720 a. For example, the session data structure 725 a caninclude a parameter field that stores a value indicating whether thesession is in the update state or the down state. In some cases, thedata repository 720 can include a parameter data structure 735 a thatstores the value indicating whether the session is in the update stateor the down state. This session state can apply or be associated with asingle session with the client 102. In some cases, this session statecan apply or be associated with one or more sessions actively managed orserviced by first device 200 a. For example, the monitor 710 a candetermine that the second device 200 b is in a standby mode and a readystate. The monitor 710 a can then then determine, responsive to thesecond device 200 b being in the ready state, to set a session statewith the update state. The monitor 710 a can store the session state asa value in the parameter data structure 735 a. The monitor 710 a can useor apply the value stored in the parameter data structure 735 a to oneor more sessions serviced by the first device 200 a. For example, if thevalue indicates that the session state is in the update state, the firstdevice 200 a can forward or replay data corresponding to packetsreceived from one or more client devices for one or more sessions to thesecond device 200 b to cause, enable, or allow the second device 200 ato maintain the state of the session in memory of the second device 200b.

The first device 200 a can receive, from a client 102 a (e.g., viaclient agent 120 a) a packet of a session that includes applicationprotocol data and application session metadata. Application protocoldata can refer to data of a state based protocol or a stateful protocol.A stateful protocol can refer to a protocol for which an internal stateis maintained on the server or an intermediary device in order for theprotocol to function or to provide access to resources. The state of asession can refer to the stored information, at a given instant in timeor subsequent to receipt and processing of a packet, to which a device,application or session has access. The state information or state of thesession or state of the application can be stored in memory in sessiondata structures 725 a-b in data repository 720 a-b. For example, thestate of the session can refer to the state of an application, state ofa desktop session, or state of a communication channel. For example, theoutput of the application at a given time can be determined by thecurrent input to the application and the state of the application.

The state of a session can refer to computer programs that operateserially (or sequentially) on streams of data, such as parsers,firewalls, communication protocols and encryption programs. Serialprograms can operate on the incoming data characters or packetssequentially, one at a time. In some of these programs, informationabout previous data characters or packets received is stored invariables in memory (e.g., in session data structure 725 a-b) and usedto affect the processing of the current character or packet by thepacket engine 715 a-b. Thus, in a stateful protocol, the data carriedover from the previous processing cycle can indicate the state or can bethe state.

When utilizing a stateful protocol, the first intermediary device orsecond intermediary device (or both) may allocate storage or memory(e.g., session data 725 a-b in data repository 720 a-b) to handleconversions in progress, or clean present states if a client fails inmid-transaction. For example, an FTP server can utilize a statefulprotocol to conduct an interactive session with a client. During thesession, a client is provided a means to be authenticated and setvarious variables (e.g., working directory or transfer mode), that canbe stored on the server or intermediary device as part of the client'sstate.

In some cases, the intermediary devices 200 a-b can manage, establish,or process interactions between stateful and stateless protocols amongdifferent protocol layers. For example, HTTP is an example of astateless protocol layered on top of TCP, a stateful protocol, which islayered on top of IP, another stateless protocol, which is routed on anetwork that employs border gateway protocol (“BGP”), another statefulprotocol, to direct the IP packets over the network.

In some embodiments, the first device 200 a can receive packets fromclient 102 over a stateful protocol. The application protocol can be astateful protocol based on TCP/IP. In some cases, the applicationprotocol can be based on one or more protocols or techniques thatprovide functionality to efficiently provide access to an application ora resource. For example, the application protocol can includefunctionality or techniques such as intelligent redirection, adaptivecompression or data de-duplication. Intelligent redirection can include,e.g., examining screen activity of the client device, examiningapplication commands, examining the server 106 being accessed, examiningcapabilities of network 104 or network 104′, or examining server 106capabilities to determine how or where to render an application ordesktop activity. For example, client redirection can offload tasks fromthe server and places them on the client. With device and peripheraldirection, webcams, printers and scanners can be terminated locally toallow client devices to interact with these devices at native USBspeeds.

In some embodiments, the application protocol can be configured toenable or provide adaptive compression. Adaptive compression can set orconfigure codecs used during different network conditions. Adaptivecompression can determine or optimize utilization of CPU or GPUresources. In some embodiments, the application protocol can beconfigured to provide de-duplication of network traffic. The applicationprotocol can facilitate de-duplication of network traffic throughmulticasting and caching techniques. For example, multicasting ofmultimedia streams can include delivering a single transmission from thesource server 106 to multiple clients 102 via one-to-manycommunications. The application protocol can use caching to de-duplicatecommonly accessed data including, e.g., bitmap graphics, files, printjobs, and streamed media. In some embodiments, the application protocolcan be or include a stateful protocol that is configured to accelerateflow of TCP-based traffic by sensing and responding to high networklatency and packet loss.

In some embodiments, the first device 200 a receives a packet of asession comprising application protocol data and application sessionmeta data. Application protocol data can refer to information such asvariables or other data that indicates the state of the session and canbe used to maintain or update the state of the session. Applicationprotocol data can include sequence identifiers for packets. Applicationprotocol data can include the data carried by a packet received from theclient device 102. In some cases, application protocol data can includedata that updates, changes, or alters the state of the session. Forexample, application protocol data can include a directory establishedfor an FTP protocol, network performance metrics for the current networksession such as packet losses or latency, the state of peripheraldevices coupled with client device, requests to access or interact witha resource, authentication information or state information in amultifactor authentication process, etc. The application session metadata can include, e.g., information that can identify the session, aprofile of the session, type of protocol being used, type of resource,an identifier of client device 102, an IP address of client device 102,source or destination addresses, server IP address, identifier of theresource being accessed, location, type of client device (e.g., mobiledevice, smartphone, laptop, desktop, or tablet), type of network (e.g.,cell phone network, 3G network, 4G network, LTE network, WIFI network,or Ethernet), time stamp corresponding to initiation of the session, orother information about the application session. Application sessionmeta data can include or be based on application protocol data. In somecases, application data can refer to application protocol data andapplication session meta data.

In some embodiments, the first device 200 a (e.g., via packet engine 715a) parses and processes the application protocol data on a per packetbasis. The first device 200 a can parse and process the applicationprotocol data and the application session meta data on a per packetbasis. The first device 200 a can parse and process the applicationprotocol or application session data to maintain a state of the sessionin memory of the first device 200 a, and to actively service the client102. When the first device 200 a receives the packet, the first devicecan further determine whether the session state is in an update state ora down state. For example, the first device 200 a (or second device 200b) may have previously marked the session state in an update state or adown state. The first device 200 a can then determine that the seconddevice 200 b is in the ready state. Responsive to determining that thesession state is in the update state and the second device 200 b is inthe ready state, the first device 200 a can forward or replay theapplication protocol data or the application session meta data (or both)to the second device 200 b. The second device 200 b, upon receiving theapplication protocol data or application session data, or both, canmaintain, on the second device, the same state of the applicationaccessed via the session provided by the first device. Thus, the firstdevice 200 a can enable or cause the second device 200 b to maintain thestate of the session in memory of the second device 200 b such that thestate of the session in memory of the second device 200 b matches thestate of the session in memory of the first device 200 a, while thefirst device 200 a actively services the client 102 during the session.

During the session established via the client and the first device 200a, the first device 200 a can malfunction, become overloaded, succumb toa denial of service attack or virus, fail, undergo maintenance orrepair, lose power, or otherwise go offline or become unresponsive dueto a software or hardware failure. When the first device 200 a goesoffline, connections established by or with the first device may be lostor reset. For example, TCP connections established by the first device200 a with the client 102 can be reset. In the event the first device200 a goes offline, the second device 200 b can automatically resume thesession with the current state of the session maintained by the firstdevice 200 a prior to the first device 200 a going offline. For example,the first device 200 a may initially be configured as the primary device200 a and the second device 200 b can be configured as the secondarydevice 200 b. When the first device 200 a goes offline, the seconddevice 200 b can become the new primary device and establish a newconnection with the client 102 to resume the session.

In some embodiments, the monitor 710 b of the second device 200 b canpoll the first device 200 a to determine a status of the first device200 a. The monitor 710 b can poll the first device 200 a based on a timeinterval or responsive to an event, condition or trigger. In someembodiments, the monitor 710 b can maintain an active connection withthe first device 200 a, such that when the first device 200 a goesoffline, the monitor 710 b can detect that the connection with the firstdevice is lost or reset. Thus, in some embodiments, the appliance pair740 can resume the session using the active-standby pair of intermediarydevices 200 a-b without using the interface 705 because theactive-standby pair can be configured such that the primary devicereceives the packets and actively services the client, the primarydevice replays packets to the secondary device to maintain the state ofthe session on the second device, and the secondary device automaticallybecomes the new primary device responsive to the secondary devicedetermining that the old primary device is offline.

In some embodiments, the interface 705 can maintain an active connectionwith the first device 200 a and second device 200 b, and determine whena device goes offline based on losing the connection. The interface 705,responsive to detecting, determining or identifying that the firstdevice 200 a is offline, can transmit a signal to the second device 200b indicating that the first device 200 a is offline. In someembodiments, the interface 705 transmits a signal to the second device200 b to instruct the second device 200 b to become the new primarydevice 200 b. The signal can further instruct the second device 200 b toenter an active mode in which the second device 200 b, being the newprimary device 200 b, actively servers the client 102.

For example, and in some embodiments, when the first device 200 a goesoffline and the connection between the first device 200 a and the client102 is lost, the client agent 120 a can initiate a session reconnect.The interface 705 can receive the session reconnect request initiated bythe client agent 120 a, and forward the session reconnect to the seconddevice 200 b because the second device 200 b is the new primary device200 b. The second device 200 b can use the state information maintainedin memory in the session data structure 725 b of the second device 200 bto seamlessly resume the session with the client 102. Because the seconddevice 200 b maintains the current state information just prior to thefirst device 200 a going offline, the second device 200 b can resume thesession with the client 102 without the user of the client device 102having to log-in to the session again. Thus, the user of the client 102may be unaware that the first device 200 a went offline because theclient agent 120 a can automatically initiate a session reconnect andthe second device 200 b can seamlessly resume the session with the samestate as the state previously maintained on the first device 200 a.Seamlessly resuming the session can refer to resuming the session withthe same state that matches the state of the session on the first device200 a prior to the first device going offline. In some embodiments,seamlessly resuming the session can refer to resuming the sessionwithout requiring a user to re-log in to the session. In someembodiments, seamlessly resuming the session can refer to resuming thesession without receiving a session reconnect request.

In some embodiments, seamlessly resuming the session can refer to thesecond device 200 b processing the last packet received by the firstdevice 200 a but not fully parsed and processed by the first device 200a (e.g., by the packet engine 715 a) due to the first device failingwhile processing the packet. Fully parsing and processing applicationprotocol data can include updating state information based on theapplication protocol data and forwarding the application protocol datato a corresponding server 106 that provides the requested resource orapplication. In some cases, the first device 200 a can replay the packetto the second device 200 b prior to parsing or processing the packet. Insome cases, the first device 200 a (e.g., via monitor 710 a) can replaythe packet to the second device 200 b while the packet engine 715 aparses and processes the packet in parallel. Thus, the packet engine 715a can processing the packet in parallel with the monitor 710 a replayingthe packet to the second device 200 b to cause the second device 200 bto maintain the session state in memory of the second device 200 b tomatch the session state of the session in memory of the first devicethat is actively servicing the client.

In some embodiments, the monitor 710 a can determine that the seconddevice is not in the ready state. The monitor 710 a can set a parameterof the session to a second value to indicate to the first device 200 ato not forward the application protocol data and application sessionmetadata to the second device. For example, the monitor 710 a can setthe value of the parameter to a down state to mark the session with thedown state. Thus, responsive to the marking the session with the downstate via the second value of the parameter, first device 710 a may notforward the application protocol data and the application sessionmetadata of a second packet of the session received from the client 102.The monitor 710 a can store, in data repository 720 a (e.g., inparameter data structure 735 a), an indication that one or more packetswere parsed or processed by the first device 200 a but not forwarded orreplayed to the second device 200 b because the session state was markedwith the down state due to the second device 200 b being in a not readystate.

Subsequent to marking the session with the down state responsive todetermining that the second device 200 a was in the unready state, themonitor 710 a can determine or detect that the second device is now inthe ready state. For example, the second device 200 a may have undergonea maintenance or repair or otherwise become online (e.g., after areset). The monitor 710 a can access the parameter data structure 735 ato update, set, modify or change the value of the parameter to indicatethat the session is in the update state. The monitor 710 a can furtherdetermine, from the parameter data structure 735 a, that one or morepackets were not forwarded or replayed to the second device 200 b. Themonitor 710 a can then determine that the state of the session on thesecond device 200 b is out-of-date. The monitor 710 a can then determineto push, forward, transmit, or otherwise provide state information tothe second device 200 b to allow the second device 200 b to update thestate of the session stored in memory of the second device 200 b suchthat the state of the session matches the state of the session in memoryof the first device 200 a. For example, the monitor 710 a can push orprovide the complete session state information to the second device 200b. The complete session state can include the application protocol dataand the application session metadata of the one or more packets notforwarded to the second device. The second device can update the statestored in memory of the second device with the complete session state tomatch a current session state maintained on the first device. In someembodiments, the monitor 710 a determines or identifies the data thatwas not replayed to the second device 200 b, and pushes thecorresponding data to the second device 200 b. In some embodiments, thefirst device 200 a determines a delta state between the first device andthe second device, and pushes the delta state information to the seconddevice 200 b. In some embodiments, the first device 200 a sends arequest to the second device 200 b to identify the last stateinformation stored on the second device 200 b.

Referring now to FIG. 7B, a block diagram of an embodiment of a methodof maintaining a session is shown. The method 750 can be performed usingone or more system or component described in FIGS. 1-7A. In briefoverview, and in some embodiments, the method 750 includes a firstdevice intermediary to a plurality of client and a plurality of serversreceiving a packet of a session including application data at step 752.At step 754, the first device determines that a second device is in aready state. At step 756, the first device marks a session state of thesession to an update state. At step 758, responsive to determining thatthe second device is in the ready state and the session state is in theupdate state, the first device forwards the application data to thesecond device to cause the second device to maintain, on the seconddevice, the same state of the session maintained on the first device.

Still referring to FIG. 7B, and in further detail, a first deviceintermediary to a plurality of clients and a plurality of serversreceives a packet of a session including application data at step 752.The first device can be a first device in an active-standby pair ofintermediary devices that includes the first device and a second device.The first device can be the active device that actively services theclient requests. The second device can be the standby device. Thus, thefirst device may be the primary device actively servicing the client,and the second device can be the secondary device in a standby mode. Thefirst device can receive a packet of a session that includes applicationprotocol data and application session metadata used to maintain a stateof an application accessed via the session.

For example, the first device can receive, from a client device or agentof the client device, an indication to launch an application provided byan application server. The first device can initiate, responsive to theindication from the client device, a connection to the applicationserver that is configured to execute the application. For example, theapplication server may be configured with the application and havesuitable computational and memory resources to execute and deliver theapplication to the client device via the first intermediary device. Thefirst device can receive log information from the client and use the login information to establish the session between the client device and aserver of the plurality of servers responsive to receiving logininformation from the client. For example, the first device can beconfigured to facilitate or perform an authentication or authorizationprocess using credentials such as username, password, biometricinformation, fingerprint, secure code, dynamic code, text-based code,audio tone, or multifactor authentication. Thus, the first device canestablish the session between the client and the server to provideaccess to the application executed by the server.

At step 754, the first device determines that a second device is in aready state and a session state of the session is in an update state.The first device can determine that the second device intermediary tothe client and the plurality of servers is in the ready state and thesession state of the session is in the update state. For example, thefirst device can poll the second device to determine a device state ofthe second device. The first device can poll the second device todetermine if the second device is in a ready state or a not ready state.The ready state can indicate that the second device is ready to parsethe application protocol data and the application session metadata tomaintain, in memory of the second device, the same state of theapplication accessed via the session provided by the first device.

In some embodiments, the second device can present or provide a statusindicator that indicates a status or state of the second device, such asready state or not ready state. In some embodiments, the first devicecan maintain an active connection with the second device and determinethat the second device is in the ready state as long as the connectionis active and online. In some embodiments, the first device can analyzeperformance characteristics associated with the connection to determinewhether the second device is in the ready state. For example, the firstdevice can use a handshaking protocol to identify a number of lostpackets, latency, or response time associated with the connection withthe second device. If the response time of the second device is below athreshold (e.g., 1 second, 2 seconds, 5 seconds, 10 seconds, 0.5seconds, 0.1 seconds, or 1 minute), then the first device can determinethat the second device is not in the ready state. If the number ofpackets dropped by the second device is above a threshold (e.g., 5, 10,25, 50, 100, 3, or 2), then the first device can determine that thesecond device is not in the ready state.

At step 756, the first device marks a session state of the session to anupdate state. For example, responsive to the first device determiningthat the second device is in the ready state, the first device can marka session state of the session to an update state. The update state canindicate or instruct the first device to forward application protocoldata and application session meta data to the second device to enable,cause or allow the second device to maintain a state of the session orapplication in memory of the second device while the first deviceactively services the client. For example, the first device can set aparameter of the session to a first value indicating to the first deviceto forward the application protocol data and the application sessionmetadata to the second device responsive to determining that the seconddevice is in the ready state. The first value can include, e.g., updatestate.

At step 758, responsive to determining that the second device is in theready state and the session state is in the update state, the firstdevice forwards the application data to the second device to cause thesecond device to maintain, on the second device, the same state of thesession maintained on the first device. The first device can forward, tothe second device, responsive to determining that the second device isin the ready state and the session is in the update state, theapplication protocol data and the application session metadata of thepacket to the second device. The first device can forward the dataresponsive to the first value of the parameter. The second device canuse this application protocol data and application session meta data tomaintain the same state of the application accessed via the sessionprovided by the first device.

For example, the first device parses the packet to actively service theclient during at least a portion of the session, while the second devicemaintains in memory of the second device, the state of the applicationaccessed via the session provided by the first device while the firstdevice actively services the client. In this configuration, the seconddevice can be configured in the standby mode, and the first device canbe configured in the active mode.

In some embodiments, the first device can enter an offline mode in whichthe first device cannot or does not actively service the client. Thefirst device may not provide the client with access to the application.When the first device enters the offline mode, the first device mayreset, lose, or disconnect one or more connections, including, e.g., theconnection with the client device. Responsive to the first deviceentering the offline mode, the mode of the second device can change fromstandby to active, and the second device can become the new primarydevice. The new primary device (or second device) can resume the sessionon the second device. For example, the second device (or new primarydevice) can retrieve, from a session data structure in memory of thesecond device, the state of the session or application and use thecurrent state of the session to process the packets received from theclient device. The state of the session retrieved from memory of thesecond device can match the state of the session in memory of the firstdevice prior to the first device entering the offline mode.

In some embodiments, the client agent executed by the client devicedetermines that the first connection between the client device and thefirst device has been terminated or ended. Responsive to determiningthat the client agent has been disconnected from the first device, theclient agent can initiate a session reconnect procedure. The clientagent can transmit a request to reconnect or re-establish the session.Since the first device is offline and no longer the primary device, thenew primary device (or second device) can receive the session reconnectrequest and establish a second connection to re-establish the sessionusing the up-to-date state information maintained in memory of thesecond device. In some embodiments, the second device can resume thesession without the second device receiving the login information fromthe client because the second device can retrieve the current stateinformation from memory of the second device. By storing and maintainingthe state information in memory of the second device, the second devicecan seamlessly, automatically, and efficiently resume the session.

In some embodiments, the first device can determine, at some pointduring the session, that the second device is no longer in the readystate. The first device can then update the marking of the session bysetting the parameter of the session to a second value such as a downstate. The second value, or down state, can indicate to the first deviceto not forward the application protocol data and application sessionmetadata to the second device. For as long as the session is marked inthe down state, the first device can determine not to forwardapplication protocol data and application session metadata of a secondpacket of the session received from the client.

During the session, and subsequent to marking the session in the downstate and determining not to forward the application protocol data andthe application session metadata of the second packet, the first devicecan detect that the second device is back in the ready state. Forexample, the second device can transmit a signal or indication to thefirst device indicating that the second device is back in the readystate. The second device can transmit the signal responsive to returningto the ready state. In some cases, the first device can poll or monitorthe second device based on a time interval. By polling or monitoring thesecond device, the first device can detect that the second devicereturned to the ready state. Polling or monitoring the device caninclude sending a ping or query to determine whether there is aconnection or determine a status of a connection or a status of thedevice.

Upon determining that the second device is in the ready state, the firstdevice can return the parameter to the first value to indicate that thesession is back in the update state. Responsive to the session being inthe update state, the first device can provide a complete session stateto the second device. The complete session state can include theapplication protocol data and the application session metadata of thesecond packet not forwarded to the second device. The first device canprovide the complete session state to the second device and can causethe second device to update the state stored in memory of the seconddevice with the complete session state to match a current session statemaintained on the first device.

In some embodiments, the session state can be set to update state ordown state based on the device state of the second device. For example,if the second device is in the ready state, then the session state canbe set to update state. In some embodiments, the session state can beset to update state or down state independent of the device state of thesecondary device. For example, the session state can be set to updatestate or down state responsive to a configuration parameter associatedwith the session, client device, application protocol, or configurationset by an administrator of the first device. For example, apredetermined configuration for a session, type of session, type ofnetwork, type of computing device, or type of application can correspondto the update state or the down state. For example, an entity may chargea larger fee for a session to be in the update state due to addedfunctionality of seamlessly resuming session. Thus, if a customer doesnot want the higher level service, the administrator of the first devicecan configure the session state to a down state such that the seconddevice does not also maintain the session state even if the seconddevice is in the ready state. Thus, the first device can forwardapplication protocol data and application session data to the seconddevice if both the session state is in the update state and the devicestate of the second device is in the ready state.

Referring now to FIG. 8A, a flow diagram 800 of an embodiment ofmaintaining a session via an intermediary device (or appliance pairincluding a first intermediary device and second intermediary device) isshown. The process 800 can be performed by one or more component orsystem depicted in FIGS. 1-7A. At step 805, a primary device of anactive-standby pair of intermediary devices receives request for a newprotocol connection from a client device, such as a stateful applicationprotocol connection. At 810, the primary device can determine if asecondary device of the active-standby pair of intermediary devices isin the ready state. If the secondary device is in the ready state,indicated by Yes 815, the primary device can mark the session to updatestate at step 820. The primary device can further forward theapplication data received from the client to the secondary device. Theapplication data can include application protocol data and applicationsession meta data. The primary device can further process and forwardthe application protocol data to the server corresponding to the requestreceived from the client device. If, however, the primary devicedetermines that the secondary device is not in the ready state,indicated by No 825, the primary device can mark the session to a downstate. The primary device can then continue to process and forward theapplication protocol data to the server corresponding to the requestreceived from the client.

Referring now to FIG. 8B, a flow diagram 801 of an embodiment ofmaintaining a session via an intermediary device (or appliance pairincluding a first intermediary device and second intermediary device) isshown. The process 801 can be performed by one or more component orsystem depicted in FIGS. 1-7A. At step 835, the primary device canreceive application protocol data. At 840, the primary device candetermine whether the session state is in the update state or the downstate. If the session is in the update state, indicated by Yes 845, theprimary device can determine if the secondary device is in the readystate at step 850. If primary device determines that the secondarydevice is in the ready state, indicated by Yes 855, the primary devicecan forward the application data (e.g., the application protocol data orapplication session meta data) to the secondary device at step 860. Theprimary device can further process and forward the protocol data 835 tothe corresponding server at step 860.

If the primary device determines that the secondary device is not in theready state, indicated by No 865, the primary device can mark thesession to down state at step 870. The primary device can furtherprocess and forward the protocol data 835 to the corresponding server atstep 870. Thus, the primary device can actively service the clientregardless of whether the secondary device is in the ready state or not.

If primary device determines that the session is not in update state,indicated by No 875, the primary device can determine whether thesecondary device is in the ready state at step 880. If the primarydevice determines that the secondary device is in the ready state,indicated by Yes 885, the primary device can mark the session to updatestate at step 890. For example, the primary device can change themarking of the session from down state to update state at 890. Theprimary device can further push the complete session state to thesecondary device at step 890. If the secondary device is in the readystate, indicated by Yes 885, the primary device can also forward theapplication data to the secondary device at step 895. The primary devicecan forward the application data to the secondary device at step 895after the primary device pushes the complete session state to thesecondary state at step 890. For example, the primary device can firstbring the secondary device up-to-date, and then forward the newapplication protocol data 835 to enable the secondary device to maintainthe state of the session in memory of the secondary device at step 895.

If the primary device determines that the secondary device is not in theready state, indicated by No 896, the primary device can proceed toprocess and forward the application protocol data 835 to thecorresponding server.

It should be understood that the systems described above may providemultiple ones of any or each of those components and these componentsmay be provided on either a standalone machine or, in some embodiments,on multiple machines in a distributed system. The systems and methodsdescribed above may be implemented as a method, apparatus or article ofmanufacture using programming and/or engineering techniques to producesoftware, firmware, hardware, or any combination thereof. In addition,the systems and methods described above may be provided as one or morecomputer-readable programs embodied on or in one or more articles ofmanufacture. The term “article of manufacture” as used herein isintended to encompass code or logic accessible from and embedded in oneor more computer-readable devices, firmware, programmable logic, memorydevices (e.g., EEPROMs, ROMs, PROMs, RAMs, SRAMs, etc.), hardware (e.g.,integrated circuit chip, Field Programmable Gate Array (FPGA),Application Specific Integrated Circuit (ASIC), etc.), electronicdevices, a computer readable non-volatile storage unit (e.g., CD-ROM,floppy disk, hard disk drive, etc.). The article of manufacture may beaccessible from a file server providing access to the computer-readableprograms via a network transmission line, wireless transmission media,signals propagating through space, radio waves, infrared signals, etc.The article of manufacture may be a flash memory card or a magnetictape. The article of manufacture includes hardware logic as well assoftware or programmable code embedded in a computer readable mediumthat is executed by a processor. In general, the computer-readableprograms may be implemented in any programming language, such as LISP,PERL, C, C++, C#, PROLOG, or in any byte code language such as JAVA. Thesoftware programs may be stored on or in one or more articles ofmanufacture as object code.

References to “or” may be construed as inclusive so that any termsdescribed using “or” may indicate any of a single, more than one, andall of the described terms.

While various embodiments of the methods and systems have beendescribed, these embodiments are exemplary and in no way limit the scopeof the described methods or systems. Those having skill in the relevantart can effect changes to form and details of the described methods andsystems without departing from the broadest scope of the describedmethods and systems. Thus, the scope of the methods and systemsdescribed herein should not be limited by any of the exemplaryembodiments and should be defined in accordance with the accompanyingclaims and their equivalents.

What is claimed is:
 1. A method, comprising: receiving, by a computingdevice comprising one or more processors and responsive to a packet of asession indicating the computing device is in a ready state, protocoldata from a second device, the second device in communication with aclient device, and the protocol data enables the client device to accessa session for an application via the second device; creating, by thecomputing device, data of a state of the application of the sessionbased at least on the protocol data; establishing, by the computingdevice, a connection with the client device in response to aninterruption of communications between the second device and the clientdevice; retrieving, by the computing device, the data of the state ofthe application from memory of the computing device in response to theconnection of the client device with the computing device, so as tocontinue the session; and initiating, by the computing device, an updateto a parameter of the session based on a change in the ready state, theupdate to the parameter to stop transmission of the protocol data to thecomputing device.
 2. The method of claim 1, wherein the protocol data isforwarded from the second device, so that the protocol data received bythe computing device is the same as protocol data used by the seconddevice to enable the client device to access the session.
 3. The methodof claim 1, further comprising receiving, by the computing device, theprotocol data from the second device responsive to a setting of a valueto the parameter in the packet of the session to indicate that thecomputing device is in the ready state.
 4. The method of claim 1,wherein the computing device and the second device are intermediary tothe client device and a third device providing the application.
 5. Themethod of claim 1, further comprising receiving, by the computingdevice, the protocol data responsive to the computing device being inthe ready state and the second device setting the parameter in thepacket of the session to a value that causes the second device toforward the protocol data to the computing device.
 6. The method ofclaim 5, wherein the computing device switches from the ready state toanother state and the parameter of the session is set to a second valuethat causes the second device not to forward the protocol data to thecomputing device.
 7. The method of claim 6, wherein responsive to theparameter of the session being set to the second value the computingdevice is no longer forwarded protocol data.
 8. An intermediary device,comprising: a memory; and one or more processors coupled to the memoryand configured to: receive protocol data from a client device, theprotocol data being configured to enable the client device via theintermediary device to access an application; identify a computingdevice in a ready state, the ready state indicative of the computingdevice being able to parse the protocol data to maintain, in memory ofthe computing device, information including a state of a session of theapplication, wherein the state of the session stored in memory of thecomputing device matches a state of the session stored in theintermediary device; provide, prior to an interruption in communicationsbetween the intermediary device and the client device, the receivedprotocol data to the computing device, so that the computing deviceparses the same protocol data as the intermediary device to maintain andupdate the information that includes the state of the session so as toshare the state of the session among different devices; and initiate anupdate to a parameter of the session based on a change in the readystate, the update to the parameter to stop transmission of the protocoldata to the computing device.
 9. The intermediary device of claim 8,wherein the protocol data is provided to the computing device, so thatthe protocol data received by the computing device is the same asprotocol data used by the intermediary device to enable the clientdevice to access the session.
 10. The intermediary device of claim 8,wherein the session is a virtual session.
 11. The intermediary device ofclaim 8, wherein the one or more processors are further configured toset, responsive to identifying that the computing device is in the readystate, the parameter of the session to a value that causes the protocoldata to be forwarded to the computing device.
 12. The intermediarydevice of claim 8, wherein the one or more processors are furtherconfigured to identify that the computing device switched from the readystate to another state.
 13. The intermediary device of claim 12, whereinthe one or more processors are further configured to set, responsive tothe computing device not being in the ready state, the parameter of thesession to a second value that causes the protocol data not to beforwarded to the computing device.
 14. The intermediary device of claim13, wherein the one or more processors are further configured to stopproviding the protocol data to the computing device responsive to theparameter of the session being set to the second value.
 15. A computingdevice, comprising: one or more processors, coupled to memory, andconfigured to: receive, responsive to a packet of a session indicatingthat the computing device is in a ready state, from a second device incommunication with a client device, protocol data that enables theclient device to access a session for an application via the seconddevice; create data of a state of the application of the session basedat least on the protocol data; establish a connection with the clientdevice in response to an interruption of communications between thesecond device and the client device; retrieve the data of the state ofthe application from memory of the computing device in response to theclient device connecting with the computing device, so as to continuethe session; and initiate an update to a parameter of the session basedon a change in the ready state, the update to the parameter to stoptransmission of the protocol data to the computing device.
 16. Thecomputing device of claim 15, wherein the protocol data is forwardedfrom the second device, so that the protocol data received by thecomputing device is the same as protocol data used by the second deviceto enable the client device to access the session.
 17. The computingdevice of claim 15, wherein the computing device and the second deviceare intermediary to the client device and a third device providing theapplication.
 18. The computing device of claim 15, wherein the one ormore processors are further configured to receive the protocol dataresponsive to the computing device being in the ready state and thesecond device setting the parameter in the packet of the session to avalue indicating to forward the protocol data to the computing device.19. The computing device of claim 18, wherein the computing deviceswitches from the ready state to another state and the parameter in thepacket of the session is set to a second value indicating to not forwardthe protocol data to the computing device.
 20. The computing device ofclaim 19, wherein responsive to the parameter of the session being setto the second value the computing device is not forwarded protocol datafrom the second device.